Detection of autoantibodies reactive with pancreatic islet cell antigenic molecules and/or insulin

ABSTRACT

A method of screening a sample of body fluid obtained from an animal subject for analyte autoantibodies reactive with one or more antigenic molecules selected from pancreatic islet cell antigenic molecules (GAD, 1A2) and insulin, or one or more variants, analogs, derivatives or fragments thereof, and a kit for use in such a method. After addition of the sample one or more complexes comprising [antigenic molecule of first source]-[analyte auto antibody]-[antigenic molecule of second source]. The antigenic molecule of first source is immobilized to a solid phase, the second is labeled.

This application is a Divisional Application of U.S. patent applicationSer. No. 13/412,419, filed 5 Mar. 2012, now U.S. Pat. No. 9,435,797,which is a Continuation Application of U.S. application Ser. No.10/496,528, now U.S. Pat. No. 8,129,132, filed 21 Sep. 2004, which is aNational Stage Application of PCT/GB2002/05285, filed 26 Nov. 2002,which claims benefit of Serial No. 0128583.2, filed 28 Nov. 2001 in theUnited Kingdom and which applications are incorporated herein byreference. To the extent appropriate, a claim of priority is made toeach of the above disclosed applications.

The present invention relates to methods and kits useful in thedetection of autoantibodies reactive with pancreatic islet cellantigenic molecules and/or insulin, for example methods and kits usefulin the detection of autoantibodies indicative of the onset or presenceof insulin dependent diabetes mellitus (IDDM, type 1 diabetes).

Type 1 diabetes is one of the more prevalent autoimmune diseasesaffecting man, with more than 2 million individuals in Europe and NorthAmerica suffering from the disease (M A Atkinson, G S Eisenbarth. Type 1diabetes: new perspectives on disease pathogenesis and treatment. TheLancet, 2001 358: 221-229). Furthermore, the incidence of type 1diabetes is increasing worldwide by 2.5% per year and it is estimatedthat the incidence of this disease will be 40% higher in 2010 that in1998 (M A Atkinson, G S Eisenbarth. Type 1 diabetes: new perspectives ondisease pathogenesis and treatment. The Lancet, 2001 358: 221-229).

Autoantibodies to pancreatic β cell antigens are well recognisedserological markers of type 1 diabetes and these include: autoantibodiesreactive with islet cells in immunofluorescence tests (ICA),autoantibodies to glutamic acid decarboxylase (GAD, in particular the 65kDa isoform thereof, GAD₆₅), autoantibodies to protein tyrosinephosphatase-like islet cell antigen (which can be referred to as IA-2 orICA512) and autoantibodies to insulin. GAD₆₅ autoantibodies and IA-2autoantibodies are components of ICA reactivity (M A Atkinson, G SEisenbarth. Type 1 diabetes: new perspectives on disease pathogenesisand treatment. The Lancet, 2001 358: 221-229). At least one of the threetypes of autoantibodies to GAD₆₅, IA-2 and insulin are present atdiagnosis in sera from about 90% of patients with type 1 diabetes (M AAtkinson, G S Eisenbarth. Type 1 diabetes: new perspectives on diseasepathogenesis and treatment. The Lancet, 2001 358: 221-229). Measurementof the above mentioned autoantibodies being serological markers ofautoimmunity to pancreatic β cells can also be useful in monitoringpatients involved in trials for prevention of diabetes (M A Atkinson, GS Eisenbarth. Type 1 diabetes: new perspectives on disease pathogenesisand treatment. The Lancet, 2001 358: 221-229).

Currently, GAD₆₅ autoantibodies are measured using immunoprecipitationassays (IPA) employing GAD₆₅ radioactively labelled with ³⁵S, ³H or¹²⁵I. GAD₆₅ labelled with ³⁵S or ³H has been produced in an in vitrotranscription/translation system (C E Grubin, T Daniels, B Toivola, MLanddin-Olsson, W A Hagopian, L Li, A E Karlsen, E Boel, B Michelsen,{acute over (Å)} Lernmark. A novel radioligand binding assay todetermine diagnostic accuracy of isoform-specific glutamic aciddecarboxylase antibodies in childhood IDDM. Diabetologia, 1994 37:344-350; J S Petersen, K R Hejnaes, A Moody, A E Karlsen, M O Marshall,M H{acute over (ø)}ier-Madsen, E Boel, B K Michelsen, T Dyrberg.Detection of GAD₆₅ antibodies in diabetes and other autoimmune diseasesusing a simple radioligand assay. Diabetes, 1994 43: 459-467; and AFalorni, E Ortqvist, B Persson, {acute over (Å)} Lernmark.Radioimmunoassays for glutamic acid decarboxylase (GAD₆₅) and GAD₆₅autoantibodies using ³⁵S or ³H recombinant human ligands. Journal ofImmunological Methods, 1995 186: 88-89). Native GAD₆₅, for example rator porcine GAD₆₅ isolated from brain tissue (M J Rowley, I R Mackay, Q-YChen, W J Knowles, P Z Zimmet. Antibodies to glutamic acid decarboxylasediscriminate major types of diabetes mellitus. Diabetes, 1992 41:548:551; and M Ohta, H Obayashi, K Takahashi, Y Kitagawa, K Nakano, SMatsuo, M Ohishi, N Itoh, K Hayashi, K Ohta. A simple solid-phaseradioimmunoassay for glutamic acid decarboxylase (GAD) antibodies inpatients with diabetes mellitus. J Clin Biochem Nutr, 1996 20: 139-148)or recombinant human GAD₆₅, for example expressed in insect cells, yeastor mammalian cells (F Lüher, K-P Woltanski, L Mauch, H Haubruck, K-DKohnert, I Rjasanowski, D Michaelis, M Ziegler. Detection ofautoantibodies to the 65-kD isoform of glutamate decarboxylase byradioimmunoassay. European Journal of Endocrinology, 1994 130: 575-80; MPowell, L Prentice, T Asawa, R Kato, J Sawicka, H Tanaka, V Petersen, AMunkley, S Morgan, B Rees Smith, J Furmaniak. Clinica Chimica Acta, 1996256: 175-188; and T Matsuba, M Yano, No Abiru, H Takino, S Akazawa, SNagataki, K Yasukawa. Expression of recombinant human glutamic aciddecarboxylase (GAD) in myeloma cells and enzyme-linked immunosorbentassay (ELISA) for autoantibodies to GAD. J Biochem, 1997 121: 20-24)have been labelled with ¹²⁵I and used in IPAs. Recombinant fusionproteins of GAD₆₅ and IA-2 have also been used in IPAs for combinedautoantibody testing (A Zavialov, M Ankelo, A Westerlund-Karlsson, MKnip, J Illonen, A Hinkkanen. Novel fusion proteins in the analysis ofdiabetes associated autoantibodies to GAD₆₅ and IA-2. Journal ofImmunological Methods, 2000 246: 91-96; and M Rickert, J Seissler, WDangel, H Lorenz, W Richter. Fusion proteins for combined analysis ofautoantibodies to the 65-kDa isoform of glutamic acid decarboxylase andislet antigen-2 in insulin dependent diabetes mellitus. ClinicalChemistry, 2001 47(5):926-934).

Currently available IPAs based on ³⁵S-GAD₆₅ have, however, beentechnically demanding, difficult to standardise, relatively expensiveand have not been adaptable to a kit format. Assays based on humanrecombinant ¹²⁵I-GAD₆₅ have been of equal sensitivity and specificity toassays based on ³⁵S-GAD₆₅, and have exhibited the added advantage ofgood reproducibility, technical simplicity, lower costs and have beeneasily adapted into a kit. Unfortunately, however, assays based on¹²⁵I-GAD₆₅ isolated from rat or porcine brain tissue have suffered fromlower specificity due to contamination with GAD₆₇ isoform.

GAD₆₅ autoantibodies have also been measured by different types ofELISAs (A M Gronowski, E C C Wong, T R Wilhite, D L Martin, C H Smith, CA Parvin, M Landt. Detection of glutamic acid decarboxylaseautoantibodies with the varelisa ELISA. Clinical Chemistry, 1995 41(10):1532-1534; and H D Mehta, B S Vold, S Minkin, E F Ullman. DELISA:sensitive nonisotopic assay for GAD₆₅ autoantibodies, a keyrisk-assessment marker for insulin-dependent diabetes mellitus. ClinicalChemistry, 1996 42(2): 263-269).

However, currently available tests to measure GAD₆₅ autoantibodies byELISA have poorer sensitivity and specificity than the above mentionedIPAs and do not compare well with the IPAs in proficiency studies (R SSchmidli, P G Colman, E Bonifacio, Participating Laboratories. Diseasesensitivity and specificity of 52 assays for glutamic acid decarboxylaseantibodies. The second international GADAb workshop. Diabetes, 1995 44:636-640).

The present invention, however, alleviates the problems hithertoassociated with methods and kits employed in the screening ofautoantibodies indicative of the onset or presence of type 1 diabetesand have general applicability in the detection of autoantibodiesreactive with pancreatic islet cell antigenic molecules and/or insulin.In particular, the present invention employs methods and kits havingimproved specificity and sensitivity when compared to prior arttechniques as discussed above.

There is provided by the present invention a method of screening asample of body fluid obtained from an animal subject for analyteautoantibodies reactive with one or more antigenic molecules selectedfrom pancreatic islet cell antigenic molecules and insulin, or one ormore variants, analogues, derivatives or fragments thereof, said methodcomprising:

-   -   (a) providing said sample of body fluid from said subject;    -   (b) providing one or more first sources of antigenic molecules        with which analyte autoantibodies when present in said sample of        body fluid can interact and which antigenic molecules are        selected from pancreatic islet cell antigenic molecules,        insulin, one or more variants, analogues, derivatives or        fragments of said pancreatic islet cell antigenic molecules or        insulin, and fusion molecules comprising two or more directly or        indirectly fused antigenic molecules selected from pancreatic        islet cell antigenic molecules, insulin and said one or more        variants, analogues, derivatives or fragments thereof;    -   (c) providing one or more second sources of antigenic molecules        with which analyte autoantibodies when present in said sample of        body fluid can interact and which antigenic molecules are        selected from pancreatic islet cell antigenic molecules,        insulin, one or more variants, analogues, derivatives or        fragments of said pancreatic islet cell antigenic molecules or        insulin, and fusion molecules comprising two or more directly or        indirectly fused antigenic molecules selected from pancreatic        islet cell antigenic molecules, insulin and said one or more        variants, analogues, derivatives or fragments thereof;    -   (d) contacting said antigenic molecules as provided by steps (b)        and (c) simultaneously or successively with said sample of body        fluid being screened, whereby analyte autoantibodies when        present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more complexes        comprising [antigenic molecule of said first source]-[analyte        autoantibody]-[antigenic molecule of said second source],        wherein said antigenic molecules of said first and second        sources when present in said one or more complexes comprise, or        are derived from, a common antigenic molecule, or wherein        binding regions of said antigenic molecules of said first and        second sources, for said analyte autoantibody, when present in        said one or more complexes are present in, or are derived from,        a common antigenic molecule;    -   (e) prior to, or concurrent with, or subsequent to, step (d),        providing immobilising means whereby said antigenic molecule of        said first source as present in a complex as formed in step (d)        is immobilised to a solid support prior to, or concurrent with,        or subsequent to, step (d);    -   (f) prior to, or concurrent with, or subsequent to, step (d),        providing direct or indirect detectable labelling means whereby        said antigenic molecule of said second source as present in a        complex as formed in step (d) is provided with such direct or        indirect detectable labelling means prior to, or concurrent        with, or subsequent to, step (d); and    -   (g) detecting the presence of complexes formed in (d)        immobilised according to (e) so as to provide an indication of        analyte autoantibodies present in said sample.

A method of screening for analyte autoantibodies according to thepresent invention is particularly advantageous in providing a method forsuch autoantibody detection of high specificity and sensitivity.

The one or more antigenic molecules, or one or more variants, analogues,derivatives or fragments thereof, or fusion molecules thereof, that canreact with analyte autoantibodies as required by the present inventioncan be selected from any pancreatic islet cell antigenic molecule andinsulin, and one or more variants, analogues, derivatives or fragmentsthereof, or fusion molecules thereof and in particular can suitably beselected from the group consisting of glutamic acid decarboxylase (GAD,and in particular the 65 KDa and 67 KDa isoforms of glutamic aciddecarboxylase, GAD₆₅ and GAD₆₇), protein tyrosine phosphatase-like isletcell antigen (IA-2) and insulin, or one or more variants (such as, forexample, IA-2 beta), analogues, derivatives or fragments thereof, orfusion molecules comprising two or more of the above, with which analyteautoantibodies when present in said sample of body fluid can interact.In a particularly, preferred embodiment of the present invention, one ormore of the above mentioned pancreatic islet cell antigenic molecules orinsulin are employed, in particular the above mentioned pancreatic isletcell antigenic molecules, preferably one or more of GAD₆₅, GAD₆₇ orIA-2. Alternatively it may be preferred that one or more variants,analogues, derivatives or fragments of one or more of the abovementioned pancreatic islet cell antigenic molecules or insulin areemployed, in particular one or more variants, analogues, derivatives orfragments of the above mentioned pancreatic islet cell antigenicmolecules, preferably one or more variants, analogues, derivatives orfragments of one or more of GAD₆₅, GAD₆₇ or IA-2. In a furtheralternative preferred embodiment of the present invention, it may bepreferred that one or more fusion molecules are employed comprising twoor more directly or indirectly fused antigenic molecules selected fromthe above mentioned pancreatic islet cell antigenic molecules, insulinand said one or more variants, analogues, derivatives or fragmentsthereof.

It will be appreciated, therefore, that the term GAD as used hereinencompasses all isoforms of GAD, including in particular GAD₆₅ or GAD₆₇and in certain embodiments of the present invention it may be preferredthat GAD₆₅ is employed and in other embodiments of the present inventionit may be preferred that GAD₆₇ is employed. It will also be appreciatedfrom the above that the present invention can include within its scopefusion molecules that can comprise GAD₆₅ or GAD₆₇, or one or morefragments thereof (such as binding regions thereof). For example, fusionmolecules for use within the scope of the present invention can compriseGAD₆₅ directly or indirectly fused to GAD₆₇, or one or more bindingregions of GAD₆₅ directly or indirectly fused to one or more bindingregions or GAD₆₇. Furthermore, it will also be appreciated that fusionmolecules for use within the scope of the present invention can compriseIA-2, or one or more binding regions thereof, directly or indirectlyfused to IA-2 beta, or one or more binding regions thereof. The presentinvention also allows for GAD₆₅ or GAD₆₇, or one or more variants,analogues, derivatives or fragments thereof, directly or indirectlyfused to IA-2, or one or more variants, analogues, derivatives orfragments thereof.

In particular the one or more antigenic molecules, or one or morevariants, analogues, derivatives or fragments thereof, that can reactwith such analyte autoantibodies as required by the present invention,can suitably be selected from the group consisting of glutamic aciddecarboxylase (in particular GAD₆₅ or GAD₆₇) and protein tyrosinephosphatase-like islet cell antigen (IA-2), or one or more variants,analogues, derivatives or fragments thereof, with which analyteautoantibodies when present in said sample of body fluid can interact.

In a preferred aspect of the present invention, therefore, a method ofscreening substantially as hereinbefore described is for use indetecting analyte autoantibodies to GAD and/or IA-2, and the one or moreantigenic molecules comprise GAD₆₅ or GAD₆₇, or one or more variants,analogues, derivatives or fragments thereof, and/or IA-2, or one or morevariants, analogues, derivatives or fragments thereof, with whichanalyte autoantibodies when present in said sample of body fluid caninteract. In the case where fusion antigenic molecules are employed inthe present invention, suitable fusion molecules may comprise GAD₆₅ orGAD₆₇ or one or more variants, analogues, derivatives or fragmentsthereof, directly or indirectly fused to IA-2, or one or more variants,analogues, derivatives or fragments thereof; alternatively, suitablefusion molecules may comprise GAD₆₅ directly or indirectly fused toGAD₆₇, or one or more binding regions of GAD₆₅ directly or indirectlyfused to one or more binding regions or GAD₆₇; alternatively suitablefusion molecules may comprise IA-2, or one or more binding regionsthereof, directly or indirectly fused to IA-2 beta, or one or morebinding regions thereof.

Preferably a method according to the present invention comprisesproviding one or more first sources of antigenic molecules selected fromGAD₆₅, GAD₆₇, IA-2, insulin, one or more variants, analogues,derivatives or fragments thereof and fusion molecules comprising two ormore directly or indirectly fused antigenic molecules selected fromGAD₆₅, GAD₆₇, IA-2, insulin and said one or more variants, analogues,derivatives or fragments thereof, with which analyte autoantibodies whenpresent in said sample of body fluid can interact, immobilised to asolid support according to step (e) of a method according to the presentinvention and one or more second sources of antigenic molecules selectedfrom GAD₆₅, GAD₆₇, IA-2, insulin, one or more variants, analogues,derivatives or fragments thereof and fusion molecules comprising two ormore directly or indirectly fused antigenic molecules selected fromGAD₆₅, GAD₆₇, IA-2, insulin and said one or more variants, analogues,derivatives or fragments thereof, with which analyte autoantibodies whenpresent in said sample of body fluid can interact, provided withlabelling means according to step (f) of a method according to thepresent invention.

More preferably, a method according to the present invention comprisesproviding one or more first sources of antigenic molecules selected fromGAD₆₅, GAD₆₇, IA-2, one or more variants, analogues, derivatives orfragments thereof and fusion molecules comprising two or more directlyor indirectly fused antigenic molecules selected from GAD₆₅, GAD₆₇,IA-2, and said one or more variants, analogues, derivatives or fragmentsthereof, with which analyte autoantibodies when present in said sampleof body fluid can interact (for example fusion molecules comprisingGAD₆₅, GAD₆₇, or one or more variants, analogues, derivatives orfragments thereof directly or indirectly fused to IA-2 or one or morevariants, analogues, derivatives or fragments thereof, with whichanalyte autoantibodies when present in said sample of body fluid caninteract), immobilised to a solid support according to step (e) of amethod according to the present invention and a second source ofantigenic molecules selected from GAD₆₅, GAD₆₇, IA-2, one or morevariants, analogues, derivatives or fragments thereof and fusionmolecules comprising two or more directly or indirectly fused antigenicmolecules selected from GAD₆₅, GAD₆₇, IA-2, and one or more variants,analogues, derivatives or fragments thereof, with which analyteautoantibodies when present in said sample of body fluid can interact(such as fusion molecules comprising GAD₆₅ or GAD₆₇, or one or morevariants, analogues, derivatives or fragments thereof directly orindirectly fused to IA-2 or one or more variants, analogues, derivativesor fragments thereof, with which analyte autoantibodies when present insaid sample of body fluid can interact), provided with labelling meansaccording to step (f) of a method according to the present invention. Itmay be preferred that where a method according to the present inventionis required to detect autoantibodies to GAD, the method comprisesproviding a first source of antigenic molecules consisting essentiallyof GAD antigenic molecules selected from GAD₆₅, GAD₆₇, one or morevariants, analogues, derivatives or fragments thereof with which analyteautoantibodies when present in said sample of body fluid can interactand fusion molecules comprising two or more directly or indirectly fusedantigenic molecules selected from GAD₆₅, GAD₆₇ and the one or morevariants, analogues, derivatives or fragments thereof, (such as fusionmolecules comprising GAD₆₅ directly or indirectly fused to GAD₆₇, or oneor more binding regions of GAD₆₅ directly or indirectly fused to one ormore binding regions or GAD₆₇, with which analyte autoantibodies whenpresent in said sample of body fluid can interact), immobilised to asolid support according to step (e) of a method according to the presentinvention and a second source of antigenic molecules consistingessentially of GAD antigenic molecules selected from GAD₆₅, GAD₆₇, oneor more variants, analogues, derivatives or fragments thereof with whichanalyte autoantibodies when present in said sample of body fluid caninteract and fusion molecules comprising two or more directly orindirectly fused antigenic molecules selected from GAD₆₅, GAD₆₇ and oneor more variants, analogues, derivatives or fragments thereof, withwhich analyte autoantibodies when present in said sample of body fluidcan interact (such as GAD₆₅ directly or indirectly fused to GAD₆₇, orone or more binding regions of GAD₆₅ directly or indirectly fused to oneor more binding regions or GAD₆₇) provided with labelling meansaccording to step (f) of a method according to the present invention.Alternatively, it may be preferred that where a method according to thepresent invention is required to detect autoantibodies to IA-2, themethod comprises providing a first source of antigenic moleculesconsisting essentially of IA-2 antigenic molecules selected from IA-2,one or more variants, analogues, derivatives or fragments thereof, withwhich analyte autoantibodies when present in said sample of body fluidcan interact and fusion molecules comprising two or more directly orindirectly fused antigenic molecules selected from IA-2 and one or morevariants, analogues, derivatives or fragments thereof, with whichanalyte autoantibodies when present in said sample of body fluid caninteract (such as IA-2, or one or more binding regions thereof, directlyor indirectly fused to IA-2 beta, or one or more binding regionsthereof) immobilised to a solid support according to step (e) of amethod according to the present invention and a second source ofantigenic molecules consisting essentially of IA-2 antigenic moleculesselected from IA-2, one or more variants, analogues, derivatives orfragments thereof with which analyte autoantibodies when present in saidsample of body fluid can interact and fusion molecules comprising two ormore directly or indirectly fused antigenic molecules selected from IA-2and one or more variants, analogues, derivatives or fragments thereof,with which analyte autoantibodies when present in said sample of bodyfluid can interact (such as IA-2, or one or more binding regionsthereof, directly or indirectly fused to IA-2 beta, or one or morebinding regions thereof), provided with labelling means according tostep (f) of a method according to the present invention. A still furtheralternative according to the present invention may be where a methodaccording to the present invention is required to detect autoantibodiesto both GAD and IA-2, where the method comprises providing (i) first andsecond sources of GAD antigenic molecules with which analyteautoantibodies when present in said sample of body fluid can interact,and which GAD antigenic molecules are selected from GAD₆₅, GAD₆₇, one ormore variants, analogues, derivatives or fragments thereof and fusionmolecules comprising two or more directly or indirectly fused antigenicmolecules selected from GAD₆₅, GAD₆₇, IA-2, and said one or morevariants, analogues, derivatives or fragments thereof and wherein atleast one of said antigenic molecules of said fusion molecule comprisesGAD₆₅, GAD₆₇, or one or more variants, analogues, derivatives orfragments thereof, wherein GAD antigenic molecules of said first sourceare immobilised to a solid support according to step (e) and GADantigenic molecules of said second source are provided with labellingmeans according to step (f); and (ii) first and second sources of IA-2antigenic molecules with which analyte autoantibodies when present insaid sample of body fluid can interact and which IA-2 antigenicmolecules are selected from IA-2, one or more variants, analogues,derivatives or fragments thereof, and fusion molecules comprising two ormore directly or indirectly fused antigenic molecules selected fromIA-2, GAD₆₅, GAD₆₇ and said one or more variants, analogues, derivativesor fragments thereof and wherein at least one of said antigenicmolecules of said fusion molecule comprises IA-2 or one or morevariants, analogues, derivatives or fragments thereof, wherein IA-2antigenic molecules of said first source are immobilised to a solidsupport according to step (e) and IA-2 antigenic molecules of saidsecond source are provided with labelling means according to step (f).

Accordingly, a preferred embodiment of the present invention maysuitably comprise a method of screening a sample of body fluid obtainedfrom an animal subject for analyte autoantibodies reactive with one ormore antigenic molecules selected from pancreatic islet cell antigenicmolecules, or one or more variants, analogues, derivatives or fragmentsthereof, said method comprising:

-   -   (a) providing said sample of body fluid from said subject;    -   (b) providing one or more first sources of antigenic molecules        with which analyte autoantibodies when present in said sample of        body fluid can interact and which antigenic molecules are        selected from GAD₆₅, GAD₆₇, IA-2, one or more variants,        analogues, derivatives or fragments thereof and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from GAD₆₅, GAD₆₇, IA-2, and said one or more        variants, analogues, derivatives or fragments thereof;    -   (c) providing one or more second sources of antigenic molecules        with which analyte autoantibodies when present in said sample of        body fluid can interact and which antigenic molecules are        selected from GAD₆₅, GAD₆₇, IA-2, one or more variants,        analogues, derivatives or fragments thereof and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from GAD₆₅, GAD₆₇, IA-2 and said one or more        variants, analogues, derivatives or fragments thereof;    -   (d) contacting said antigenic molecules as provided by steps (b)        and (c) simultaneously or successively with said sample of body        fluid being screened, whereby analyte autoantibodies when        present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more complexes        comprising [antigenic molecule of said first source]-[analyte        autoantibody]-[antigenic molecule of said second source],        wherein said antigenic molecules of said first and second        sources when present in said one or more complexes comprise, or        are derived from, a common antigenic molecule, or wherein        binding regions of said antigenic molecules of said first and        second sources, for said analyte autoantibody, when present in        said one or more complexes are present in, or are derived from,        a common antigenic molecule;    -   (e) prior to, or concurrent with, or subsequent to, step (d),        providing immobilising means whereby said antigenic molecule of        said first source as present in a complex as formed in step (d)        is immobilised to a solid support prior to, or concurrent with,        or subsequent to, step (d);    -   (f) prior to, or concurrent with, or subsequent to, step (d),        providing direct or indirect detectable labelling means whereby        said antigenic molecule of said second source as present in a        complex as formed in step (d) is provided with such direct or        indirect detectable labelling means prior to, or concurrent        with, or subsequent to, step (d); and    -   (g) detecting the presence of complexes formed in (d)        immobilised according to (e) so as to provide an indication of        analyte autoantibodies present in said sample.

Alternatively, a preferred embodiment of the present invention maysuitably comprise screening a sample of body fluid obtained from ananimal subject for analyte autoantibodies reactive only with GAD, or oneor more variants, analogues, derivatives or fragments thereof, saidmethod comprising:

-   -   (a) providing said sample of body fluid from said subject;    -   (b) providing first and second sources of antigenic molecules        consisting essentially of GAD antigenic molecules selected from        GAD₆₅, GAD₆₇, one or more variants, analogues, derivatives or        fragments thereof with which analyte autoantibodies when present        in said sample of body fluid can interact and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from GAD₆₅, GAD₆₇ and said one or more        variants, analogues, derivatives or fragments thereof, wherein        GAD antigenic molecules of said first source are immobilised to        a solid support according to step (d) and GAD antigenic        molecules of said second source are provided with labelling        means according to step (e);    -   (c) contacting said antigenic molecules as provided by step (b)        simultaneously or successively with said sample of body fluid        being screened, whereby analyte autoantibodies when present in        said sample of body fluid can interact with said antigenic        molecules so as to form one or more complexes comprising [GAD        antigenic molecule of said first source]-[analyte        autoantibody]-[GAD antigenic molecule of said second source];    -   (d) prior to, or concurrent with, or subsequent to, step (c),        providing immobilising means whereby said GAD antigenic molecule        of said first source as present in a complex as formed in        step (c) is immobilised to a solid support prior to, or        concurrent with, or subsequent to, step (c);    -   (e) prior to, or concurrent with, or subsequent to, step (c),        providing direct or indirect detectable labelling means whereby        said GAD antigenic molecule of said second source as present in        a complex as formed in step (c) is provided with such direct or        indirect detectable labelling means prior to, or concurrent        with, or subsequent to, step (c); and    -   (f) detecting the presence of complexes formed in (c)        immobilised according to (d) so as to provide an indication of        analyte autoantibodies present in said sample.

Alternatively, a preferred embodiment of the present invention maysuitably comprise screening a sample of body fluid obtained from ananimal subject for analyte autoantibodies reactive with IA-2, or one ormore variants, analogues, derivatives or fragments thereof, said methodcomprising:

-   -   (a) providing said sample of body fluid from said subject;    -   (b) providing first and second sources of antigenic molecules        consisting essentially of IA-2 antigenic molecules selected from        IA-2, one or more variants, analogues, derivatives or fragments        thereof with which analyte autoantibodies when present in said        sample of body fluid can interact and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from IA-2 and said one or more variants,        analogues, derivatives or fragments thereof, wherein IA-2        antigenic molecules of said first source are immobilised to a        solid support according to step (d) and IA-2 antigenic molecules        of said second source are provided with labelling means        according to step (e);    -   (c) contacting said IA-2 antigenic molecules as provided by        step (b) simultaneously or successively with said sample of body        fluid being screened, whereby analyte autoantibodies when        present in said sample of body fluid can interact with said IA-2        antigenic molecules so as to form one or more complexes        comprising [IA-2 antigenic molecule of said first        source]-[analyte autoantibody]-[IA-2 antigenic molecule of said        second source];    -   (d) prior to, or concurrent with, or subsequent to, step (c),        providing immobilising means whereby said IA-2 antigenic        molecule of said first source as present in a complex as formed        in step (c) is immobilised to a solid support prior to, or        concurrent with, or subsequent to, step (c);    -   (e) prior to, or concurrent with, or subsequent to, step (c),        providing direct or indirect detectable labelling means whereby        said IA-2 antigenic molecule of said second source as present in        a complex as formed in step (c) is provided with such direct or        indirect detectable labelling means prior to, or concurrent        with, or subsequent to, step (c); and    -   (f) detecting the presence of complexes formed in (c)        immobilised according to (d) so as to provide an indication of        analyte autoantibodies present in said sample.

Alternatively, a preferred embodiment of the present invention maysuitably comprise screening a sample of body fluid obtained from ananimal subject for first and second analyte autoantibodies respectivelyreactive with GAD and IA-2, or one or more variants, analogues,derivatives or fragments thereof, said method comprising:

-   -   (a) providing said sample of body fluid from said subject;    -   (b) providing first and second sources of GAD antigenic        molecules with which analyte autoantibodies when present in said        sample of body fluid can interact, and which GAD antigenic        molecules are selected from GAD₆₅, GAD₆₇, one or more variants,        analogues, derivatives or fragments thereof and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from GAD₆₅, GAD₆₇, IA-2, and said one or more        variants, analogues, derivatives or fragments thereof and        wherein at least one of said antigenic molecules of said fusion        molecule comprises GAD₆₅, GAD₆₇, or one or more variants,        analogues, derivatives or fragments thereof, wherein GAD        antigenic molecules of said first source are immobilised to a        solid support according to step (e) and GAD antigenic molecules        of said second source are provided with labelling means        according to step (f);    -   (c) providing first and second sources of IA-2 antigenic        molecules with which analyte autoantibodies when present in said        sample of body fluid can interact and which IA-2 antigenic        molecules are selected from IA-2, one or more variants,        analogues, derivatives or fragments thereof, and fusion        molecules comprising two or more directly or indirectly fused        antigenic molecules selected from IA-2, GAD₆₅, GAD₆₇ and said        one or more variants, analogues, derivatives or fragments        thereof and wherein at least one of said antigenic molecules of        said fusion molecule comprises IA-2 or one or more variants,        analogues, derivatives or fragments thereof, wherein IA-2        antigenic molecules of said first source are immobilised to a        solid support according to step (e) and IA-2 antigenic molecules        of said second source are provided with labelling means        according to step (f);    -   (d) contacting said antigenic molecules as provided by steps (b)        and (c) simultaneously or successively with said sample of body        fluid being screened, whereby analyte autoantibodies when        present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more complexes        comprising [GAD antigenic molecule of said first        source]-[analyte autoantibody]-[GAD antigenic molecule of said        second source] or [IA-2 antigenic molecule of said first        source]-[analyte autoantibody]-[IA-2 antigenic molecule of said        second source];    -   (e) prior to, or concurrent with, or subsequent to, step (d),        providing immobilising means whereby said GAD or IA-2 antigenic        molecule of said first source as present in a complex as formed        in step (d) is immobilised to a solid support prior to, or        concurrent with, or subsequent to, step (d);    -   (f) prior to, or concurrent with, or subsequent to, step (d),        providing direct or indirect detectable labelling means whereby        said GAD or IA-2 antigenic molecule of said second source as        present in a complex as formed in step (d) is provided with such        direct or indirect detectable labelling means prior to, or        concurrent with, or subsequent to, step (d); and    -   (g) detecting the presence of complexes formed in (d)        immobilised according to (e) so as to provide an indication of        analyte autoantibodies present in said sample.

It may be preferred in a method according to the present invention thatthe antigenic molecules of the first and second sources when present insaid one or more complexes substantially as hereinbefore described bothcomprise one or more common antigenic molecules. For example, antigenicmolecules of said first and second sources when present in the one ormore complexes can comprise GAD₆₅ or GAD₆₇; alternatively the antigenicmolecules of the first and second sources when present in the one ormore complexes can comprise IA-2.

Alternatively, it may be preferred that one antigenic molecule, ofeither the first or second source, when present in the one or morecomplexes comprises an antigenic molecule selected from pancreatic isletcell antigenic molecules and insulin, and the other antigenic moleculewhen present in the one or more complexes comprises one or morevariants, analogues, derivatives or fragments of the above mentioned oneantigenic molecule with which analyte autoantibodies when present insaid sample of body fluid can interact. For example, where one of theantigenic molecules of the first or second source when present in theone or more complexes comprises GAD₆₅ or GAD₆₇, the other antigenicmolecule when present in the one or more complexes can comprise one ormore variants, analogues, derivatives or fragments of GAD₆₅ or GAD₆₇with which analyte autoantibodies when present in said sample of bodyfluid can interact. A further example may be where one of the antigenicmolecules of the first or second source when present in the one or morecomplexes comprises IA-2, and the other antigenic molecule when presentin the one or more complexes can comprise one or more variants,analogues, derivatives or fragments of IA-2 with which analyteautoantibodies when present in said sample of body fluid can interact.

A still further alternative embodiment of the present invention may bewhere both antigenic molecules of the first and second sources whenpresent in the one or more complexes comprise a variant, analogue,derivative or fragment, which may be the same or different, of a commonantigenic molecule, with which analyte autoantibodies when present insaid sample of body fluid can interact. For example, both antigenicmolecules of the first and second sources when present in the one ormore complexes can comprise a variant, analogue, derivative or fragment,which may be the same or different, of GAD₆₅ or GAD₆₇, with whichanalyte autoantibodies when present in said sample of body fluid caninteract. A further example may be where both antigenic molecules of thefirst and second sources when present in said one or more complexescomprise a variant, analogue, derivative or fragment, which may be thesame or different, of IA-2, with which analyte autoantibodies whenpresent in said sample of body fluid can interact. It will beappreciated from the above that where both antigenic molecules whenpresent in the complexes formed according to a method of the presentinvention comprise variants, analogues, derivatives or fragments derivedfrom a common antigenic molecule, such variants, analogues, derivativeor fragments may be the same or different (for example variant 1 andvariant 2, where variants 1 and 2 may respectively represent differentvariants of GAD₆₅ or GAD₆₇, or fragment 1 and fragment 2, wherefragments 1 and 2 may respectively represent different fragments ofGAD₆₅ or GAD₆₇, such as distinct, or possibly overlapping, epitopes ofGAD₆₅ or GAD₆₇).

In the case where fusion molecules are employed in a method according tothe present invention, it will be appreciated that such fusion moleculescan comprise distinct antigenic molecules (for example GAD₆₅ and IA-2)but that in a complex formed according to the present invention thebinding regions of antigenic fusion molecules for an analyteautoantibody as respectively provided by the first and second sourceswill be present in, or will be derived from, a common antigenicmolecule. Examples of complexes that may be formed employing one or morefusion molecules according to the present invention can include (i)[GAD-IA-2_(imm)]-[analyte autoantibody]-[GAD-IA-2_(label)] where in thecase where the autoantibody comprises a GAD autoantibody thisautoantibody interacts with binding regions of GAD present in[GAD-IA-2_(imm)] and [GAD-IA-2_(label)], or where the autoantibodycomprises a IA-2 autoantibody this autoantibody interacts with bindingregions of IA-2 present in [GAD-IA-2_(imm)] and [GAD-IA-2_(label)], or(ii) [GAD(fragment)_(imm)]-[analyte autoantibody]-[GAD-IA-2_(label)]where a GAD analyte autoantibody interacts with binding regions of GADpresent in [GAD(fragment)_(imm)] and [GAD-IA-2_(label)], or (iii)[IA-2(fragment)_(imm)]-[analyte autoantibody]-[GAD-IA-2_(label)] where aIA-2 analyte autoantibody interacts with binding regions of IA-2 presentin [IA-2(fragment)_(imm)] and [GAD-IA-2_(label)], where GAD canrepresent GAD₆₅ or GAD₆₇.

Suitably the detectable labelling means can be selected from the groupconsisting of enzymic labels, isotopic labels, chemiluminescent labels,fluorescent labels, dyes and the like and typically can be selected fromthe group consisting of alkaline phosphatase, horseradish peroxidase,biotin or the like and in particular can comprise biotin. The monitoringcan typically involve reaction of such detectable labelling means (whenattached to the one or more antigenic molecules substantially ashereinbefore described, or one or more variants, analogues, derivativesor fragments thereof, or one or more fusion molecules thereof) with oneor more substrates therefor (such as an avidin or streptavidinconjugate, for example, streptavidin horseradish peroxidase conjugate orthe like), whereby the resulting conjugates can be detected suitably bymeasurement of optical density or the like.

The detectable labelling means may be directly provided to the one ormore antigenic molecules, or one or more one or more variants,analogues, derivatives or fragments thereof, or one or more fusionmolecules thereof, substantially as hereinbefore described. Additionallyor alternatively the detectable labelling means may be indirectlyprovided to the one or more antigenic molecules, or one or more one ormore variants, analogues, derivatives or fragments thereof, or one ormore fusion molecules thereof, substantially as hereinbefore described,typically by providing the detectable labelling means to one or moreantibodies or other binding agents which can bind with the one or moreantigenic molecules, or one or more variants, analogues, derivatives orfragments thereof, or one or more fusion molecules thereof,substantially as hereinbefore described.

A method of screening for autoantibodies according to the presentinvention typically comprises directly monitoring interaction of (i)such autoantibodies present in the sample of body fluid from the subjectand (ii) one or more antigenic molecules, or one or more variants,analogues, derivatives or fragments thereof, or one or more fusionmolecules thereof, substantially as hereinbefore described, as providedby the present invention, typically by employing non-competitivesandwich type assay techniques known in the art.

According to a preferred embodiment of the present invention antigenicmolecules of one or more first sources, or one or more variants,analogues, derivatives or fragments thereof, or one or more fusionmolecules thereof, substantially as hereinbefore described, areimmobilised to a solid support and antigenic molecules of one or moresecond sources, or one or more variants, analogues, derivatives orfragments thereof, or one or more fusion molecules thereof,substantially as hereinbefore described, are provided with detectablelabelling means, and wherein preferably the antigenic molecules of theone or more second sources are provided in solution phase as isconventional for use in known ELISA techniques.

Preferably, in a method according to the present invention, antigenicmolecules, or one or more variants, analogues, derivatives or fragmentsthereof, or one or more fusion molecules thereof, with which analyteautoantibodies when present in said sample of body fluid can interact,of one or more first sources are immobilised to a solid support prior tocontact with a sample of body fluid being screened. Such immobilisedantigenic molecules of the one or more first sources, or more one ormore variants, analogues, derivatives or fragments thereof, or one ormore fusion molecules thereof, with which analyte autoantibodies whenpresent in said sample of body fluid can interact, are subsequentlycontacted with the sample of body fluid being screened eithersimultaneously or successively with contact of the sample of body fluidwith antigenic molecules of one or more second sources, or one or morevariants, analogues, derivatives or fragments thereof, or one or morefusion molecules thereof, with which analyte autoantibodies when presentin said sample of body fluid can interact. Particularly preferably,immobilised antigenic molecules of the one or more first sources, or oneor more variants, analogues, derivatives or fragments thereof, or one ormore fusion molecules thereof, with which analyte autoantibodies whenpresent in said sample of body fluid can interact, are contacted withthe sample of body fluid being screened so as to form an intermediatecomplex comprising [antigenic molecule]-[analyte autoantibody] where theantigenic molecule is immobilised to a solid support and the thus formedimmobilised intermediate complex is subsequently contacted withantigenic molecules of the one or more second sources, or one or morevariants, analogues, derivatives or fragments thereof, or one or morefusion molecules thereof, with which analyte autoantibodies when presentin said sample of body fluid can interact, present in solution phase, soas to form the hitherto described complexes comprising [antigenicmolecule of said first source]-[analyte autoantibody]-[antigenicmolecule of said second source] immobilised to a solid support via theantigenic molecule of the first source.

Accordingly, the present invention provides a method of screening asample of body fluid obtained from an animal subject for analyteautoantibodies reactive with one or more antigenic molecules selectedfrom pancreatic islet cell antigenic molecules and insulin, or one ormore variants, analogues, derivatives or fragments thereof, said methodcomprising:

-   -   (a) providing said sample of body fluid from said subject;    -   (b) providing one or more first sources of antigenic molecules        with which analyte autoantibodies when present in said sample of        body fluid can interact and which antigenic molecules are        selected from pancreatic islet cell antigenic molecules,        insulin, one or more variants, analogues, derivatives or        fragments of said pancreatic islet cell antigenic molecules or        insulin, and fusion molecules comprising two or more directly or        indirectly fused antigenic molecules selected from pancreatic        islet cell antigenic molecules, insulin and said one or more        variants, analogues, derivatives or fragments thereof, which        antigenic molecules of said one or more first sources are        immobilised to a solid support;    -   (c) providing one or more second sources of antigenic molecules        with which analyte autoantibodies when present in said sample of        body fluid can interact and which antigenic molecules are        selected from pancreatic islet cell antigenic molecules,        insulin, one or more variants, analogues, derivatives or        fragments of said pancreatic islet cell antigenic molecules or        insulin, and fusion molecules comprising two or more directly or        indirectly fused antigenic molecules selected from pancreatic        islet cell antigenic molecules, insulin and said one or more        variants, analogues, derivatives or fragments thereof, which        antigenic molecules of said one or more second sources are        provided in solution phase;    -   (d) contacting said antigenic molecules as provided by steps (b)        and (c) simultaneously or successively with said sample of body        fluid being screened, whereby analyte autoantibodies when        present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more immobilised        complexes comprising [antigenic molecule of said first        source]-[analyte autoantibody]-[antigenic molecule of said        second source], wherein said antigenic molecules of said first        and second sources when present in said one or more complexes        comprise, or are derived from, a common antigenic molecule, or        wherein binding regions of said antigenic molecules of said        first and second sources, for said analyte autoantibody, when        present in said one or more complexes are present in, or are        derived from, a common antigenic molecule and wherein said        complexes are immobilised to a solid support via said antigenic        molecule of said first source;    -   (e) prior to, or concurrent with, or subsequent to, step (d),        providing direct or indirect detectable labelling means whereby        said antigenic molecule of said second source as present in a        complex as formed in step (d) is provided with such direct or        indirect detectable labelling means prior to, or concurrent        with, or subsequent to, step (d); and    -   (f) detecting the presence of complexes formed in (d) so as to        provide an indication of analyte autoantibodies present in said        sample.

The one or more antigenic molecules, or one or more variants, analogues,derivatives or fragments thereof, or fusion molecules thereof, that canreact with analyte autoantibodies as required by the present inventioncan be selected from any pancreatic islet cell antigenic molecule andinsulin, and one or more variants, analogues, derivatives or fragmentsthereof, or fusion molecules thereof and in particular can suitably beselected from the group consisting of glutamic acid decarboxylase (GAD,and in particular the 65 KDa and 67 KDa isoforms of glutamic aciddecarboxylase, GAD₆₅ and GAD₆₇), protein tyrosine phosphatase-like isletcell antigen (IA-2) and insulin, or one or more variants (such as, forexample, IA-2 beta), analogues, derivatives or fragments thereof, orfusion molecules comprising two or more of the above, with which analyteautoantibodies when present in said sample of body fluid can interact.In particular the one or more antigenic molecules, or one or morevariants, analogues, derivatives or fragments thereof, that can reactwith such analyte autoantibodies as required by the present invention,can suitably be selected from the group consisting of glutamic aciddecarboxylase (GAD, in particular GAD₆₅ or GAD₆₇) and protein tyrosinephosphatase-like islet cell antigen (IA-2), or one or more variants,analogues, derivatives or fragments thereof, with which analyteautoantibodies when present in said sample of body fluid can interact.

Other contacting techniques are, however, possible, for example it ispossible according to the present invention not to initially immobilisethe antigenic molecules, or one or more variants, analogues, derivativesor fragments thereof, or one or more fusion molecules thereof, of theone or more first antigen sources, prior to a contacting step asdescribed above, but to initially contact the solid supportsubstantially as hereinbefore described with a binder for the antigenicmolecules, or one or more variants, analogues, derivatives or fragmentsthereof, or one or more fusion molecules thereof, of the one or morefirst antigen sources and to subsequently contact the so treated solidsupport with the above described antigenic molecules of the one or morefirst and second sources, or one or more variants, analogues,derivatives or fragments thereof, or one or more fusion moleculesthereof, and the sample of body fluid being screened.

In respect of the solid supports and conditions employed in the presentinvention, the supports and conditions do not generally fundamentallydiffer from conventional supports and conditions employed in knownimmunoassay techniques. A solid support for use according to the presentinvention can comprise an ELISA plate as currently employed in knownELISA techniques, or may employ any other suitable support for use inthe present invention, such as tubes, particles, magnetic beads,nitrocellulose or the like.

There is also provided by the present invention a kit for screening asample of body fluid obtained from an animal subject for analyteautoantibodies reactive with one or more antigenic molecules selectedfrom pancreatic islet cell antigenic molecules and insulin, or one ormore variants, analogues, derivatives or fragments thereof, said kitcomprising:

-   -   (a) one or more first sources of antigenic molecules with which        analyte autoantibodies when present in said sample of body fluid        can interact and which antigenic molecules are selected from        pancreatic islet cell antigenic molecules, insulin, one or more        variants, analogues, derivatives or fragments of said pancreatic        islet cell antigenic molecules or insulin, and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from pancreatic islet cell antigenic        molecules, insulin and said one or more variants, analogues,        derivatives or fragments thereof;    -   (b) one or more second sources of antigenic molecules with which        analyte autoantibodies when present in said sample of body fluid        can interact and which antigenic molecules are selected from        pancreatic islet cell antigenic molecules, insulin, one or more        variants, analogues, derivatives or fragments of said pancreatic        islet cell antigenic molecules or insulin, and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from pancreatic islet cell antigenic        molecules, insulin and said one or more variants, analogues,        derivatives or fragments thereof;    -   (c) means for contacting said antigenic molecules as provided        by (a) and (b) simultaneously or successively with said sample        of body fluid being screened, whereby analyte autoantibodies        when present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more complexes        comprising [antigenic molecule of said first source]-[analyte        autoantibody]-[antigenic molecule of said second source],        wherein said antigenic molecules of said first and second        sources when present in said one or more complexes comprise, or        are derived from, a common antigenic molecule, or wherein        binding regions of said antigenic molecules of said first and        second sources, for said analyte autoantibody, when present in        said one or more complexes are present in, or are derived from,        a common antigenic molecule;    -   (d) means for immobilising to a solid support, said antigenic        molecule of said first source as present in a complex as defined        in (c), prior to, or concurrent with, or subsequent to, contact        of the antigenic molecule of said first source with the sample        of body fluid being screened;    -   (e) means for providing direct or indirect detectable labelling        means to said antigenic molecule of said second source as        present in a complex as defined in (c), prior to, or concurrent        with, or subsequent to, contact of said antigenic molecule of        said second source with said sample of body fluid being        screened; and    -   (f) means for detecting the presence of complexes as defined        in (c) immobilised as defined in (d) so as to provide an        indication of analyte autoantibodies present in said sample.

A kit for screening for analyte autoantibodies according to the presentinvention is particularly advantageous in enabling such autoantibodydetection of high specificity and sensitivity.

The one or more antigenic molecules, or one or more variants, analogues,derivatives or fragments thereof, or fusion molecules thereof, that canreact with analyte autoantibodies as required by the present inventioncan be selected from any pancreatic islet cell antigenic molecule andinsulin, and one or more variants, analogues, derivatives or fragmentsthereof, or fusion molecules thereof and in particular can suitably beselected from the group consisting of glutamic acid decarboxylase (GAD,and in particular the 65 KDa and 67 KDa isoforms of glutamic aciddecarboxylase, GAD₆₅ and GAD₆₇), protein tyrosine phosphatase-like isletcell antigen (IA-2) and insulin, or one or more variants (such as, forexample, IA-2 beta), analogues, derivatives or fragments thereof, orfusion molecules comprising two or more of the above, with which analyteautoantibodies when present in said sample of body fluid can interact.In particular the one or more antigenic molecules, or one or morevariants, analogues, derivatives or fragments thereof, that can reactwith such analyte autoantibodies as required by the present invention,can suitably be selected from the group consisting of glutamic aciddecarboxylase (GAD, in particular GAD₆₅ or GAD₆₇) and protein tyrosinephosphatase-like islet cell antigen (IA-2), or one or more variants,analogues, derivatives or fragments thereof, with which analyteautoantibodies when present in said sample of body fluid can interact.Various embodiments of the antigenic molecules and suitable fusionmolecules for use in a kit according to the present invention aresubstantially as hereinbefore described in greater detail with referenceto a method according to the present invention.

In a preferred aspect of the present invention, therefore, a kit forscreening substantially as hereinbefore described is for use indetecting analyte autoantibodies to GAD₆₅ or GAD₆₇ and/or IA-2, or oneor more variants, analogues, derivatives or fragments thereof, and theone or more antigenic molecules comprise GAD₆₅ or GAD₆₇, or one or morevariants, analogues, derivatives or fragments thereof, and/or IA-2, orone or more variants, analogues, derivatives or fragments thereof. Inthe case where fusion antigenic molecules are employed in a kitaccording to the present invention, suitable fusion molecules maycomprise two or more directly or indirectly fused antigenic moleculesselected from GAD₆₅, GAD₆₇, IA-2 and said one or more variants,analogues, derivatives or fragments thereof substantially ashereinbefore described in greater detail with reference to a methodaccording to the present invention.

Preferably a kit according to the present invention comprises one ormore first sources of antigenic molecules selected from GAD₆₅, GAD₆₇,IA-2, insulin, one or more variants, analogues, derivatives or fragmentsthereof, and fusion molecules comprising two or more directly orindirectly fused antigenic molecules selected from GAD₆₅, GAD₆₇, IA-2,insulin and said one or more variants, analogues, derivatives orfragments thereof, with which analyte autoantibodies when present insaid sample of body fluid can interact, immobilised to a solid supportas defined in (d) and one or more second sources of antigenic moleculesselected from GAD₆₅, GAD₆₇, IA-2, insulin, one or more variants,analogues, derivatives or fragments thereof, and fusion moleculescomprising two or more directly or indirectly fused antigenic moleculesselected from GAD₆₅, GAD₆₇, IA-2, insulin and one or more variants,analogues, derivatives or fragments thereof, with which analyteautoantibodies when present in said sample of body fluid can interact,provided with labelling means as defined in (e).

More preferably, a kit according to the present invention comprises oneor more first sources of antigenic molecules selected from GAD₆₅, GAD₆₇,IA-2, one or more variants, analogues, derivatives or fragments thereofand fusion molecules comprising two or more directly or indirectly fusedantigenic molecules selected from GAD₆₅, GAD₆₇, IA-2 and said one ormore variants, analogues, derivatives or fragments thereof, with whichanalyte autoantibodies when present in said sample of body fluid caninteract, immobilised to a solid support as defined in (d) and one ormore second sources of antigenic molecules selected from GAD₆₅, GAD₆₇,IA-2, one or more variants, analogues, derivatives or fragments thereofand fusion molecules comprising two or more directly or indirectly fusedantigenic molecules selected from GAD₆₅, GAD₆₇, IA-2 and said one ormore variants, analogues, derivatives or fragments thereof, with whichanalyte autoantibodies when present in said sample of body fluid caninteract, provided with labelling means as defined in (e). It may bepreferred that a kit according to the present invention comprises afirst source of antigenic molecules consisting essentially of GADantigenic molecules selected from GAD₆₅, GAD₆₇, one or more variants,analogues, derivatives or fragments thereof and fusion moleculescomprising two or more directly or indirectly fused antigenic moleculesselected from GAD₆₅, GAD₆₇ and said one or more variants, analogues,derivatives or fragments thereof, with which analyte autoantibodies whenpresent in said sample of body fluid can interact, immobilised to asolid support as defined in (d), and a second source of antigenicmolecules consisting essentially of GAD antigenic molecules selectedfrom GAD₆₅, GAD₆₇, one or more variants, analogues, derivatives orfragments thereof and fusion molecules comprising two or more directlyor indirectly fused antigenic molecules selected from GAD₆₅, GAD₆₇ andsaid one or more variants, analogues, derivatives or fragments thereof,with which analyte autoantibodies when present in said sample of bodyfluid can interact, provided with labelling means as defined in (e).Alternatively, it may be preferred that a kit according to the presentinvention comprises a first source of antigenic molecules consistingessentially of IA-2 antigenic molecules selected from IA-2, one or morevariants, analogues, derivatives or fragments thereof, with whichanalyte autoantibodies when present in said sample of body fluid caninteract and fusion molecules comprising two or more directly orindirectly fused antigenic molecules selected from IA-2 and said one ormore variants, analogues, derivatives or fragments thereof, immobilisedto a solid support as defined in (d), and a second source of antigenicmolecules consisting essentially of IA-2 antigenic molecules selectedfrom IA-2, one or more variants, analogues, derivatives or fragmentsthereof, with which analyte autoantibodies when present in said sampleof body fluid can interact and fusion molecules comprising two or moredirectly or indirectly fused antigenic molecules selected from IA-2 andsaid one or more variants, analogues, derivatives or fragments thereof,provided with labelling means as defined in (e). A still furtheralternative according to the present invention may be where a kitaccording to the present invention comprises (i) first and secondsources of GAD antigenic molecules with which analyte autoantibodieswhen present in said sample of body fluid can interact, and which GADantigenic molecules are selected from GAD₆₅, GAD₆₇, one or morevariants, analogues, derivatives or fragments thereof and fusionmolecules comprising two or more directly or indirectly fused antigenicmolecules selected from GAD₆₅, GAD₆₇, IA-2 and said one or morevariants, analogues, derivatives or fragments thereof and wherein atleast one of said antigenic molecules of said fusion molecule comprisesGAD₆₅, GAD₆₇, or one or more variants, analogues, derivatives orfragments thereof, wherein GAD antigenic molecules of said first sourceare immobilised to a solid support as defined in (d) and GAD antigenicmolecules of said second source are provided with labelling means asdefined in (e); and (ii) first and second sources of IA-2 antigenicmolecules with which analyte autoantibodies when present in said sampleof body fluid can interact and which IA-2 antigenic molecules areselected from IA-2, one or more variants, analogues, derivatives orfragments thereof, and fusion molecules comprising two or more directlyor indirectly fused antigenic molecules selected from IA-2, GAD₆₅, GAD₆₇and said one or more variants, analogues, derivatives or fragmentsthereof and wherein at least one of said antigenic molecules of saidfusion molecule comprises IA-2 or one or more variants, analogues,derivatives or fragments thereof, wherein IA-2 antigenic molecules ofsaid first source are immobilised to a solid support according asdefined in (d) and IA-2 antigenic molecules of said second source areprovided with labelling means as defined in (e).

Accordingly, a preferred embodiment of the present invention maysuitably comprise a kit for screening a sample of body fluid obtainedfrom an animal subject for analyte autoantibodies reactive with one ormore antigenic molecules selected from pancreatic islet cell antigenicmolecules, or one or more variants, analogues, derivatives or fragmentsthereof, said kit comprising:

-   -   (a) one or more first sources of antigenic molecules with which        analyte autoantibodies when present in said sample of body fluid        can interact and which antigenic molecules are selected from        GAD₆₅, GAD₆₇, IA-2, one or more variants, analogues, derivatives        or fragments thereof and fusion molecules comprising two or more        directly or indirectly fused antigenic molecules selected from        GAD₆₅, GAD₆₇, IA-2 and said one or more variants, analogues,        derivatives or fragments thereof;    -   (b) one or more second sources of antigenic molecules with which        analyte autoantibodies when present in said sample of body fluid        can interact and which antigenic molecules are selected from        GAD₆₅, GAD₆₇, IA-2, one or more variants, analogues, derivatives        or fragments thereof and fusion molecules comprising two or more        directly or indirectly fused antigenic molecules selected from        GAD₆₅, GAD₆₇, IA-2 and said one or more variants, analogues,        derivatives or fragments thereof;    -   (c) means for contacting said antigenic molecules as provided        by (a) and (b) simultaneously or successively with said sample        of body fluid being screened, whereby analyte autoantibodies        when present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more complexes        comprising [antigenic molecule of said first source]-[analyte        autoantibody]-[antigenic molecule of said second source],        wherein said antigenic molecules of said first and second        sources when present in said one or more complexes comprise, or        are derived from, a common antigenic molecule, or wherein        binding regions of said antigenic molecules of said first and        second sources, for said analyte autoantibody, when present in        said one or more complexes are present in, or are derived from,        a common antigenic molecule;    -   (d) means for immobilising to a solid support said antigenic        molecule of said first source as present in a complex as defined        in (c), prior to, or concurrent with, or subsequent to, contact        of said antigenic molecule of said first source with the sample        of body fluid being screened;    -   (e) means for providing direct or indirect detectable labelling        means to said antigenic molecule of said second source as        present in a complex as defined in (c), prior to, or concurrent        with, or subsequent to, contact of said antigenic molecule of        said second source with the sample of body fluid being screened;        and    -   (f) means for detecting the presence of complexes as defined        in (c) immobilised as defined in (d) so as to provide an        indication of analyte autoantibodies present in said sample.

Alternatively, a preferred embodiment of the present invention maysuitably comprise a kit for screening a sample of body fluid obtainedfrom an animal subject for analyte autoantibodies reactive with GAD, orone or more variants, analogues, derivatives or fragments thereof, saidkit comprising:

-   -   (a) first and second sources of antigenic molecules consisting        essentially of GAD antigenic molecules selected from GAD₆₅,        GAD₆₇, one or more variants, analogues, derivatives or fragments        thereof with which analyte autoantibodies when present in said        sample of body fluid can interact and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from GAD₆₅, GAD₆₇ and said one or more        variants, analogues, derivatives or fragments thereof, wherein        GAD antigenic molecules of said first source are immobilised to        a solid support as defined in (c) and GAD antigenic molecules of        said second source are provided with labelling means as defined        in (d);    -   (b) means for contacting said antigenic molecules as provided        by (a) simultaneously or successively with said sample of body        fluid being screened, whereby analyte autoantibodies when        present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more complexes        comprising [GAD antigenic molecule of said first        source]-[analyte autoantibody]-[GAD antigenic molecule of said        second source];    -   (c) means for immobilising to a solid support said GAD antigenic        molecule of said first source as present in a complex as defined        in (b), prior to, or concurrent with, or subsequent to, contact        of said GAD antigenic molecule of said first source with the        sample of body fluid being screened;    -   (d) means for providing direct or indirect detectable labelling        means to said GAD antigenic molecule of said second source as        present in a complex as defined in (b), prior to, or concurrent        with, or subsequent to, contact of said GAD antigenic molecule        of said second source with the sample of body fluid being        screened; and    -   (e) means for detecting the presence of complexes as defined        in (b) immobilised as defined in (c) so as to provide an        indication of analyte autoantibodies present in said sample.

Alternatively, a preferred embodiment of the present invention maysuitably comprise a kit for screening a sample of body fluid obtainedfrom an animal subject for analyte autoantibodies reactive with IA-2, orone or more variants, analogues, derivatives or fragments thereof, saidkit comprising:

-   -   (a) first and second sources of antigenic molecules consisting        essentially of IA-2 antigenic molecules selected from IA-2, one        or more variants, analogues, derivatives or fragments thereof,        with which analyte autoantibodies when present in said sample of        body fluid can interact and fusion molecules comprising two or        more directly or indirectly fused antigenic molecules selected        from IA-2 and said one or more variants, analogues, derivatives        or fragments thereof, wherein IA-2 antigenic molecules of said        first source are immobilised to a solid support as defined        in (c) and IA-2 antigenic molecules of said second source are        provided with labelling means as defined in (d);    -   (b) means for contacting said IA-2 antigenic molecules as        provided by (a) simultaneously or successively with said sample        of body fluid being screened, whereby analyte autoantibodies        when present in said sample of body fluid can interact with said        IA-2 antigenic molecules so as to form one or more complexes        comprising [IA-2 antigenic molecule of said first        source]-[analyte autoantibody]-[IA-2 antigenic molecule of said        second source];    -   (c) means for immobilising to a solid support said IA-2        antigenic molecule of said first source as present in a complex        as defined in (b), prior to, or concurrent with, or subsequent        to, contact of said IA-2 antigenic molecule of said first source        with the sample of body fluid being screened;    -   (d) means for providing direct or indirect detectable labelling        means to said IA-2 antigenic molecule of said second source as        present in a complex as defined in (b), prior to, or concurrent        with, or subsequent to, contact of said IA-2 antigenic molecule        of said second source with the sample of body fluid being        screened; and    -   (e) means for detecting the presence of complexes as defined        in (b) immobilised as defined in (c) so as to provide an        indication of analyte autoantibodies present in said sample.

Alternatively, a preferred embodiment of the present invention maysuitably comprise a kit for screening a sample of body fluid obtainedfrom an animal subject for first and second analyte autoantibodiesrespectively reactive with GAD and IA-2, or one or more variants,analogues, derivatives or fragments thereof, said kit comprising:

-   -   (a) first and second sources of GAD antigenic molecules with        which analyte autoantibodies when present in said sample of body        fluid can interact, and which GAD antigenic molecules are        selected from GAD₆₅, GAD₆₇, one or more variants, analogues,        derivatives or fragments thereof and fusion molecules comprising        two or more directly or indirectly fused antigenic molecules        selected from GAD₆₅, GAD₆₇, IA-2 and said one or more variants,        analogues, derivatives or fragments thereof and wherein at least        one of said antigenic molecules of said fusion molecule        comprises GAD₆₅, GAD₆₇, or one or more variants, analogues,        derivatives or fragments thereof, wherein GAD antigenic        molecules of said first source are immobilised to a solid        support as defined in (d) and GAD antigenic molecules of said        second source are provided with labelling means as defined in        (e);    -   (b) first and second sources of IA-2 antigenic molecules with        which analyte autoantibodies when present in said sample of body        fluid can interact and which IA-2 antigenic molecules are        selected from IA-2, one or more variants, analogues, derivatives        or fragments thereof, and fusion molecules comprising two or        more directly or indirectly fused antigenic molecules selected        from IA-2, GAD₆₅, GAD₆₇ and said one or more variants,        analogues, derivatives or fragments thereof and wherein at least        one of said antigenic molecules of said fusion molecule        comprises IA-2 or one or more variants, analogues, derivatives        or fragments thereof, wherein IA-2 antigenic molecules of said        first source are immobilised to a solid support according as        defined in (d) and IA-2 antigenic molecules of said second        source are provided with labelling means as defined in (e);    -   (c) means for contacting said antigenic molecules as provided        by (a) and (b) simultaneously or successively with said sample        of body fluid being screened, whereby analyte autoantibodies        when present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more complexes        comprising [GAD antigenic molecule of said first        source]-[analyte autoantibody]-[GAD antigenic molecule of said        second source] or [IA-2 antigenic molecule of said first        source]-[analyte autoantibody]-[IA-2 antigenic molecule of said        second source];    -   (d) means for immobilising to a solid support said GAD or IA-2        antigenic molecule of said first source as present in a complex        as defined in (c), prior to, or concurrent with, or subsequent        to, contact of said GAD or IA-2 antigenic molecule of said first        source with the sample of body fluid being screened;    -   (e) means for providing direct or indirect detectable labelling        means to said GAD or IA-2 antigenic molecule of said second        source as present in a complex as defined in (c), prior to, or        concurrent with, or subsequent to, contact of said GAD or IA-2        antigenic molecule of said second source with the sample of body        fluid being screened; and    -   (f) means for detecting the presence of complexes as defined        in (c) immobilised as defined in (d) so as to provide an        indication of analyte autoantibodies present in said sample.

It may be preferred in a kit according to the present invention that theantigenic molecules of the first and second sources comprise one or morecommon antigenic molecules. For example, antigenic molecules of saidfirst and second sources may comprise GAD₆₅ or GAD₆₇; alternativelyantigenic molecules of the first and second sources may both compriseIA-2.

Alternatively, it may be preferred that the antigenic molecules, ofeither the first or second source, are selected from pancreatic isletcell antigenic molecules and insulin, and the antigenic molecules of theother source comprises one or more variants, analogues, derivatives orfragments of the above mentioned antigenic molecules of either the firstor second source, with which analyte autoantibodies when present in saidsample of body fluid can interact. For example, where the antigenicmolecules of either the first or second source comprise GAD₆₅ or GAD₆₇,the antigenic molecules of the other source comprise one or morevariants, analogues, derivatives or fragments of GAD₆₅ or GAD₆₇ withwhich analyte autoantibodies when present in said sample of body fluidcan interact. A further example may be where the antigenic molecules ofeither the first or second source comprise IA-2, and the antigenicmolecules of the other source comprise one or more variants, analogues,derivatives or fragments of IA-2 with which analyte autoantibodies whenpresent in said sample of body fluid can interact.

A still further alternative embodiment of the present invention may bewhere both antigenic molecules of the first and second sources comprisea variant, analogue, derivative or fragment, which may be the same ordifferent, of a common antigenic molecule, with which analyteautoantibodies when present in said sample of body fluid can interact.For example, antigenic molecules of both the first and second sourcescan comprise a variant, analogue, derivative or fragment, which may bethe same or different, of GAD₆₅ or GAD₆₇, with which analyteautoantibodies when present in said sample of body fluid can interact. Afurther example may be where antigenic molecules of both the first andsecond sources comprise a variant, analogue, derivative or fragment,which may be the same or different, of IA-2, with which analyteautoantibodies when present in said sample of body fluid can interact.It will be appreciated from the above that where antigenic molecules ofthe first and second sources comprise variants, analogues, derivativesor fragments derived from a common antigenic molecule, such variants,analogues, derivative or fragments as provided by the respectivesources, may be the same or different (for example variant 1 provided bythe first source of antigenic molecules and variant 2 provided by thesecond source of antigenic molecules, where variants 1 and 2 mayrespectively represent different variants of GAD₆₅ or GAD₆₇, or fragment1 provided by the first source of antigenic molecules and fragment 2provided by the second source of antigenic molecules, where fragments 1and 2 may respectively represent different fragments of GAD₆₅ or GAD₆₇,such as distinct, or possibly overlapping, epitopes of GAD₆₅ or GAD₆₇).

Suitably the detectable labelling means can be selected from the groupconsisting of enzymic labels, isotopic labels, chemiluminescent labels,fluorescent labels, dyes and the like and typically can be selected fromthe group consisting of alkaline phosphatase, horseradish peroxidase,biotin or the like and in particular can comprise biotin. Suitably suchdetectable labelling means (when attached to the one or more antigenicmolecules substantially as hereinbefore described, or one or morevariants, analogues, derivatives or fragments thereof, or one or morefusion molecules thereof) can be reacted with one or more substratestherefor (such as an avidin or streptavidin conjugate, for example,streptavidin horseradish peroxidase conjugate or the like), whereby theresulting conjugates can be detected suitably by measurement of opticaldensity or the like.

The detectable labelling means may be directly provided to the one ormore antigenic molecules, or one or more one or more variants,analogues, derivatives or fragments thereof, or one or more fusionmolecules thereof, substantially as hereinbefore described. Additionallyor alternatively the detectable labelling means may be indirectlyprovided to the one or more antigenic molecules, or one or morevariants, analogues, derivatives or fragments thereof, or one or morefusion molecules thereof, substantially as hereinbefore described,typically by providing the detectable labelling means to one or moreantibodies or other binding agents which can bind with the one or moreantigenic molecules, or one or more variants, analogues, derivatives orfragments thereof, or one or more fusion molecules thereof,substantially as hereinbefore described.

A kit for screening for autoantibodies according to the presentinvention typically further comprises means for directly monitoringinteraction of (i) such autoantibodies present in the sample of bodyfluid from the subject and (ii) one or more antigenic molecules, or oneor more variants, analogues, derivatives or fragments thereof, or one ormore fusion molecules thereof, substantially as hereinbefore described,as provided by the present invention, typically by employingnon-competitive sandwich type assay techniques known in the art.

According to a preferred embodiment of the present invention antigenicmolecules of one or more first sources, or one or more variants,analogues, derivatives or fragments thereof, or one or more fusionmolecules thereof, substantially as hereinbefore described, areimmobilised to a solid support and antigenic molecules of one or moresecond sources, or one or more variants, analogues, derivatives orfragments thereof, or one or more fusion molecules thereof,substantially as hereinbefore described, are provided with detectablelabelling means, and wherein preferably the antigenic molecules of theone or more second sources are provided in solution phase as isconventional for use in known ELISA techniques.

Preferably, a kit according to the present invention comprisesimmobilising means whereby antigenic molecules, or one or more variants,analogues, derivatives or fragments thereof, or one or more fusionmolecules thereof, with which analyte autoantibodies when present insaid sample of body fluid can interact, of one or more first sources areimmobilised to a solid support prior to contact with a sample of bodyfluid being screened. Suitably a kit according to the present inventioncomprises contacting means whereby such immobilised antigenic moleculesof the one or more first sources, or one or more variants, analogues,derivatives or fragments thereof, or one or more fusion moleculesthereof, with which analyte autoantibodies when present in said sampleof body fluid can interact, can be contacted with the sample of bodyfluid being screened either simultaneously or successively with contactof the sample of body fluid with antigenic molecules of one or moresecond sources, or more one or more variants, analogues, derivatives orfragments thereof, or one or more fusion molecules thereof, with whichanalyte autoantibodies when present in said sample of body fluid caninteract. Particularly preferably, contacting means are provided wherebyimmobilised antigenic molecules of the one or more first sources, or oneor more variants, analogues, derivatives or fragments thereof, or one ormore fusion molecules thereof, with which analyte autoantibodies whenpresent in said sample of body fluid can interact, are contacted withthe sample of body fluid being screened so as to form an intermediatecomplex comprising [antigenic molecule]-[analyte autoantibody] where theantigenic molecule is immobilised to a solid support and the thus formedimmobilised intermediate complex is subsequently contacted withmolecules of the one or more second sources, or one or more variants,analogues, derivatives or fragments thereof, or one or more fusionmolecules thereof, with which analyte autoantibodies when present insaid sample of body fluid can interact, present in solution phase, so asto form the hitherto described complex comprising [antigenic molecule ofsaid first source]-[analyte autoantibody]-[antigenic molecule of saidsecond source] immobilised to a solid support via the antigenic moleculeof said first source.

Accordingly, the present invention provides a kit for screening a sampleof body fluid obtained from an animal subject for analyte autoantibodiesreactive with one or more antigenic molecules selected from pancreaticislet cell antigenic molecules and insulin, or one or more variants,analogues, derivatives or fragments thereof, said kit comprising:

-   -   (a) one or more first sources of antigenic molecules with which        analyte autoantibodies when present in said sample of body fluid        can interact and which antigenic molecules are selected from        pancreatic islet cell antigenic molecules, insulin, one or more        variants, analogues, derivatives or fragments of said pancreatic        islet cell antigenic molecules or insulin, and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from pancreatic islet cell antigenic        molecules, insulin and said one or more variants, analogues,        derivatives or fragments thereof, wherein said antigenic        molecules of said one or more first sources are immobilised to a        solid support;    -   (b) one or more second sources of antigenic molecules with which        analyte autoantibodies when present in said sample of body fluid        can interact and which antigenic molecules are selected from        pancreatic islet cell antigenic molecules, insulin, one or more        variants, analogues, derivatives or fragments of said pancreatic        islet cell antigenic molecules or insulin, and fusion molecules        comprising two or more directly or indirectly fused antigenic        molecules selected from pancreatic islet cell antigenic        molecules, insulin and said one or more variants, analogues,        derivatives or fragments thereof, which antigenic molecules of        said one or more second sources are provided in solution phase        and are provided with labelling means as defined in (d);    -   (c) means for contacting said antigenic molecules as provided        by (a) and (b) simultaneously or successively with said sample        of body fluid being screened, whereby analyte autoantibodies        when present in said sample of body fluid can interact with said        antigenic molecules so as to form one or more immobilised        complexes comprising [antigenic molecule of said first        source]-[analyte autoantibody]-[antigenic molecule of said        second source], wherein said antigenic molecules of said first        and second sources when present in said one or more complexes        comprise, or are derived from, a common antigenic molecule, or        wherein binding regions of said antigenic molecules of said        first and second sources, for said analyte autoantibody, when        present in said one or more complexes are present in, or are        derived from, a common antigenic molecule, which immobilised        complexes are immobilised to a solid support via said antigenic        molecule of said first source present in said complex;    -   (d) means for providing direct or indirect detectable labelling        means to said antigenic molecule of said second source as        present in a complex as defined in (c), prior to, or concurrent        with, or subsequent to, contact of said antigenic molecule of        said second source with said sample of body fluid being        screened; and    -   (e) means for detecting the presence of complexes as defined        in (c) so as to provide an indication of analyte autoantibodies        present in said sample.

Other contacting means may, however, be present in a kit according tothe present invention, for example it is possible according to thepresent invention not to provide means for initially immobilising theantigenic molecules, or one or more variants, analogues, derivatives orfragments thereof, or one or more fusion molecules thereof, of the oneor more first antigen sources, prior to a contacting step as describedabove, but to provide means to initially contact the solid supportsubstantially as hereinbefore described with a binder for the antigenicmolecules, or one or more variants, analogues, derivatives or fragmentsthereof, or one or more fusion molecules thereof, of the one or morefirst antigen sources and for the kit to comprise means for subsequentlycontacting the so treated solid support with the above describedantigenic molecules or the one or more first and second sources, or oneor more variants, analogues, derivatives or fragments thereof, or one ormore fusion molecules thereof, and the sample of body fluid beingscreened.

In respect of the solid supports and conditions employed in a kitaccording to the present invention, the supports and conditions do notgenerally fundamentally differ from conventional supports and conditionsemployed in known immunoassay techniques. A solid support for use in akit according to the present invention can comprise an ELISA plate ascurrently employed in known ELISA techniques, or may employ any othersuitable support for use in the present invention, such as tubes,particles, magnetic beads, nitrocellulose or the like.

Detection of analyte autoantibodies reactive with one or more antigenicmolecules selected from pancreatic islet cell antigenic molecules andinsulin according to a method provided by the present invention, oremploying a kit provided by the present invention, can be useful in thediagnosis of a number of disease states with which the presence of suchanalyte autoantibodies is associated. In particular, the presentinvention can be employed in screening a sample of body fluid from ananimal subject suspected of suffering from, susceptible to or having anyof the following disease states—type 1 diabetes mellitus and/or stiffman syndrome, type 2 diabetes mellitus, one or more autoimmune thyroiddiseases, celiac disease, one or more connective tissue diseases,adrenal autoimmunity, or a combination of two or more differentautoimmune diseases and the present invention further provides a methodof diagnosing any of the above disease states in an animal subject.

It will be appreciated from the foregoing description that the presentinvention provides assay methods and kits for detecting, in a sample ofbody fluid obtained from an animal subject, analyte autoantibodiesreactive with one or more antigenic molecules selected from pancreaticislet cell antigenic molecules and insulin and indicative of the onsetor presence of the above disease states. The detection of suchautoantibodies in the sample of body fluid (or at least the level ofsuch autoantibodies in the sample) is indicative of the likely onset orpresence of such disease states in the subject from which the sample isobtained and can, therefore, enable the diagnosis of the likely onset orpresence of such disease states.

There is, therefore, further provided by the present invention a methodof diagnosing the likely onset or presence of disease states, associatedwith the presence of autoantibodies reactive with one or more antigenicmolecules selected from pancreatic islet cell antigenic molecules andinsulin, in an animal subject (in particular a human subject), suspectedof having or being susceptible to these disease states, the methodcomprising detecting autoantibodies reactive with one or more antigenicmolecules selected from pancreatic islet cell antigenic molecules andinsulin, and being indicative of the likely onset or presence of thesedisease states in a sample of body fluid from the subject substantiallyas hereinbefore described, and whereby the detected autoantibodies canprovide a diagnosis of the likely onset or presence of these diseasestates.

There is, therefore, still further provided by the present invention amethod of delaying or preventing the onset of disease states, associatedwith the presence of autoantibodies reactive with one or more antigenicmolecules selected from pancreatic islet cell antigenic molecules andinsulin, in an animal subject (in particular a human subject), ortreating an animal subject (in particular a human subject) having orrecovering from such disease states, which method comprises initiallydetecting autoantibodies reactive with one or more antigenic moleculesselected from pancreatic islet cell antigenic molecules and insulin, andbeing indicative of the onset or presence of such disease states, in asample of body fluid obtained from the subject substantially ashereinbefore described, thereby providing a diagnosis of the likelyonset or presence of such disease states in the subject, andadministering to the subject a therapeutically effective amount of atleast one therapeutic agent effective in delaying onset, obviating,preventing and/or treating these disease states.

There is, therefore, still further provided by the present invention amethod of assessing the effectiveness of delaying or preventing theonset of disease states, associated with the presence of autoantibodiesreactive with one or more antigenic molecules selected from pancreaticislet cell antigenic molecules and insulin, in an animal subject (inparticular a human subject), or assessing the effectiveness of treatingan animal subject (in particular a human subject) having or recoveringfrom such disease states, which method comprises administering to thesubject a therapeutically effective amount of at least one therapeuticagent effective in delaying onset, obviating, preventing and/or treatingsuch disease states associated with the presence of autoantibodiesreactive with one or more antigenic molecules selected from pancreaticislet cell antigenic molecules and insulin, and detecting autoantibodiesindicative of the onset or presence of such disease states in a sampleof body fluid obtained from the subject, so as to provide an indicationof the presence of said autoantibodies in said sample, thereby providingan indication of the effectiveness of treating the subject, or ofdelaying or preventing the onset of such disease states in the subject.

There is still further provided by the present invention, incombination, a kit substantially as hereinbefore described, togetherwith a therapeutically effective amount of at least one therapeuticagent effective in the treatment of disease states associated with thepresence of autoantibodies reactive with one or more antigenic moleculesselected from pancreatic islet cell antigenic molecules and insulin.

A sample of body fluid being screened by the present invention willtypically comprise blood samples or other fluid blood fractions, such asin particular serum samples or plasma samples, but the sample may inprinciple be another biological fluid, such as saliva or urine orsolubilised tissue extracts.

The term “antigen” or “antigenic molecules” as used herein denotes acompound with which antibodies as described herein can interact andwhich is capable of binding to an antibody to form specificantibody-antigen complexes. The antigen or antigenic molecules may benatural or synthetic and modifications thereto are preferably such as tonot detrimentally affect the binding properties thereof to a specificantibody.

As indicated above, the present invention covers the use of “variants”,“analogs”, “derivatives” and “fragments” of antigenic molecules asdescribed herein and the terms “variants”, “analogs”, “derivatives” and“fragments” as used herein can be characterised as polypeptides whichretain essentially the same biological function or activity as naturallyoccurring antigenic molecules and in particular in respect of thebinding properties thereof for a specific antibody. Suitably, variants,analogs, derivatives and fragments, and variants, analogs andderivatives of the fragments as described herein, have a primarystructural conformation of amino acids in which several or a few (suchas 5 to 10, 1 to 5 or 1 to 3) amino acid residues of the naturallyoccurring antigenic molecules are substituted, deleted or added, in anycombination. Especially preferred among these are silent substitutions,additions are deletions which do not alter or substantially alter thebiological activity or function of the naturally occurring antigenicmolecules. Conservative substitutions can be preferred as hereinafterdescribed in greater detail.

More particularly, variants, analogs or derivatives of antigenicmolecules suitable for use according to the present invention may beones in which one or more of the amino acid residues are substitutedwith a conserved or non-conserved amino acid residue (preferably aconserved amino acid residue), or ones in which one or more of the aminoacid resides includes a substituent group or the like. Such variants,derivatives and analogs are deemed to be within the scope of thoseskilled in the art from the teachings herein.

Most typically, variants, analogs or derivatives are those that varyfrom a reference (such as naturally occurring antigenic molecules asreferred to herein) by conservative amino acid substitutions. Suchsubstitutions are those that substitute a given amino acid in apolypeptide by another amino acid of like characteristics. Typicallyseen as conservative substitutions are the replacements, one foranother, among the aliphatic amino acids A, V, L and I; among thehydroxyl residues S and T; among the acidic residues D and E; among theamide residues N and Q; among the basic residues K and R; and among thearomatic residues F and Y.

More particularly, the term “fragment” as used herein denotes apolypeptide having an amino acid sequence that entirely is the same aspart but not all of the amino acid sequence of naturally occurring aminoacids as referred to herein, and variants or derivatives thereof andsuch fragments may be “free standing”, i.e. not part of or fused toother amino acids or polypeptides, or they may be comprised within alarger polypeptide of which they form a part or region. In the contextof the present invention, it will be appreciated that particularlypreferred fragments for use according to the present invention may beone or more epitopes of antigenic molecules as referred to herein and asdescribed above such epitope fragments may be used in “free standing”form or may be used within a larger polypeptide, such as a scaffoldpolypeptide, of which they form a part or region. The use of suchepitope fragments in substantially isolated or free standing formaccording to the present invention can be advantageous in terms ofenhanced stability of such substantially isolated or free standingepitope fragments when compared with the use of a full length antigenand/or enhanced specificity associated with the use of suchsubstantially isolated or free standing epitope fragments compared withthe use of a full length antigen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows a calibration curve for GAD₆₅ at 450 nm.

FIG. 1b shows a calibration curve for GAD₆₅ at 405 nm.

The present invention will now be further illustrated by the followingexample, which does not limit the scope of the invention in any way.

EXAMPLE Preparation of GAD₆₅ Coated ELISA Plates

Human recombinant GAD₆₅ of >95% purity as assessed by SDS-PAGE (MPowell, L Prentice, T Asawa, R Kato, J Sawicka, H Tanaka, V Petersen, AMunkley, S Morgan, B Rees Smith, J Furmaniak. Clinica Chimica Acta, 1996256: 175-188) was diluted to 150 μg/L in a coating buffer comprising1.59 g/L Na₂CO₃, 2.94 g/L NaHCO₃, 0.1 g/L NaN₃, 0.01 g/L Phenol Red, and5 mg/L BSA (pH 9.2) and 150 μL of the resulting solution was added to96-well ELISA plates (available under the trade mark Nunc F8 MaxiSorp).The plates were then incubated overnight at 4° C., the contents of thewells aspirated and the wells washed three times with a high salt buffer(HSB) comprising 10 g/L BSA, 1 g/L NaN₃, 11.69 g/L NaCl, 18.17 g/L Tris,and 10 mL/L Polyoxyethylene-Sorbitan Monolaurate (available under thetrade mark Tween 20 (pH 8.3). A post-coat buffer comprising 3 g/L BSA, 9g/L NaCl, 20 g/L sucrose and 0.2 g/L NaN₃ was added to the wells (250 μLper well) and incubated for 30 minutes at room temperature. Thepost-coat buffer was then aspirated, the plates dried under vacuum andstored in sealed bags with silica gel at 4° C. until use.

Labelling of GAD₆₅ with Biotin

Human recombinant GAD₆₅ in PBS (1.15 g/L Na₂HPO₄, 0.2 g/L KH₂PO₄, 0.2g/L KCl, 8 g/L NaCl) was reacted with a commercial biotinylation reagent(Sulfo-NHS-LC-LC-Biotin available under the trade mark EZ-Link fromPerbio Science), at a molar ratio of 1 part GAD₆₅ to 24 partsbiotinylation reagent for 30 minutes at room temperature. The reactionwas stopped by dialysis against PBS at 4° C. and the resulting materialwas stored at −70° C. in small aliquots.

The resulting GAD₆₅ labelled with biotin according to the abovetechniques (GAD₆₅-Bi) was diluted to 3 mg/L in 20 g/L BSA, filteredthrough a 0.22 μm filter, aliquotted at 1 mL per vial, freeze dried andthen stored at −20° C. To use, 7.5 mL of HSB was added to the vial,giving a final concentration of GAD₆₅-Bi of 400 μg/L.

Preparation of Calibrators for GAD₆₅ Autoantibody Assay

IgG preparations of three human monoclonal autoantibodies to GAD₆₅ (M JPowell, N Hayakawa, M Masuda, J Sanders, M Evans, LDKE Premawardhana, JFurmaniak, B Rees Smith. Isolation and characterization of three humanmonoclonal antibodies to glutamic acid decarboxylase (GAD₆₅) from apatient without clinical diabetes. Diabetes/Metabolism Research andReviews, 2001 17 (S1): 021) were diluted in HSB to give an absorbance atOD450 nm from 4.0 to 0.1. These monoclonal antibodies are known to berepresentative of GAD₆₅ autoantibodies found in sera from patients withtype 1 diabetes (M J Powell, N Hayakawa, M Masuda, J Sanders, M Evans,LDKE Premawardhana, J Furmaniak, B Rees Smith. Isolation andcharacterization of three human monoclonal antibodies to glutamic aciddecarboxylase (GAD₆₅) from a patient without clinical diabetes.Diabetes/Metabolism Research and Reviews, 2001 17 (S1): 021).

GAD₆₅ Autoantibody Detection

Plates coated with GAD₆₅ prepared according to the above techniques werebrought to room temperature and 25 μL of undiluted serum sample obtainedfrom test donors, or calibrators prepared according to the abovetechniques, were added to the plate wells in duplicate and incubated for1 hour at room temperature with shaking at 200 rpm. The samples werethen aspirated, the wells washed three times with buffer (8.7 g/L NaCl,2.4 g/L Tris, 0.5 mL/L Tween 20, pH 7.6), followed by addition of 1004,of GAD₆₅-Bi diluted in HSB (400 μg/L) prepared according to the abovetechniques and incubation for 1 hour at room temperature, with shakingat 200 rpm. After the incubation the contents of the wells wereaspirated and wells washed three times with buffer (8.7 g/L NaCl, 2.4g/L Tris, 0.5 mL/L Tween 20, pH 7.6). Thereafter, 100 μL of astreptavidin horseradish peroxidase conjugate diluted to 1 μg/mL wasadded and incubated for 20 minutes at room temperature, with shaking at200 rpm. After aspiration, the wells were washed three times with buffer(8.7 g/L NaCl, 2.4 g/L Tris, 0.5 mL/L Tween 20, pH 7.6) and once withwater. 100 μL of tetramethyl benzidine was then added and incubated for20 minutes in the dark, followed by addition of 50 μL of 0.5 mol/LH₂SO₄. The absorbance of the wells was then measured in an ELISA platereader at 450 nm or in the case of samples giving an OD 450 nm>4.0,absorbance was also measured at 405 nm.

The above procedures were applied to IA-2 autoantibodies and also to thecombined detection of GAD₆₅ and IA-2 autoantibodies (in particular,involving the preparation of IA-2 labelled with biotin, IA-2-Bi).Reference preparations of IA-2 autoantibodies for generation of acalibration curve were prepared from polyclonal IA-2 autoantibodies.

Results

A typical calibration curve for GAD₆₅ obtained at OD 450 nm is shown inFIG. 1a . Seven calibrators of arbitrarily assigned GAD₆₅ autoantibodyELISA units from 0 ELISA units/mL to 512 ELISA units/mL were included.OD 450 nm values for the calibrators were 0.033, 0.168, 0.310, 1.020,3.187, >4.0 and >4.0 for calibrators 0, 1.0, 2.0, 8.0, 32, 128 and 512respectively. OD 405 nm values were 0.008, 0.048, 0.090, 0.290, 0.929,1.385 and 1.620 for calibrators 0, 1.0, 2.0, 8.0, 32, 128 and 512respectively as shown in FIG. 1b . Consequently, samples that gave OD450 nm values >4.0 could be measured within the calibration curve rangeat OD 405 nm as shown in FIG. 1b . The mean±SD absorbance at 450 nm forn=25 sera from healthy blood donors was 0.04±0.015.

Results of GAD₆₅ autoantibody measurement according to the presentinvention are shown in Tables 1 and 2. Results of GAD₆₅ autoantibodiesin sera from n=18 patients with type 1 diabetes mellitus and n=14patients with Graves' disease are shown in Table 1. All 18 diabetic serawere positive for GAD₆₅ autoantibodies when ELISA based techniquesaccording to the present invention were employed (levels >1.0 ELISAunits/mL), however only 13 of these patients were positive inradioimmunoassay (RIA). The 5 samples which were negative in RIA showedlow levels of GAD₆₅ autoantibodies in ELISA based techniques accordingto the present invention with OD 450 nm between 0.117 to 0.980 (1.3 to10.7 ELISA units/mL). In the case of samples with low levels in RIA (1.0to 7.5 RIA units/mL), the OD 450 nm values in ELISA based techniquesaccording to the present invention were between 0.290 and 1.060 (12.0 to105.8 ELISA units/mL). In the case of samples with higher levels ofGAD₆₅ autoantibodies in RIA (26.8 to 118.8 RIA units/mL), OD 450 nm inELISA based techniques according to the present invention were veryhigh>4.0(>128 ELISA units/mL) and, therefore, the relationship betweenthe GAD₆₅ autoantibody levels in the sample and the calibration curvewas calculated after measurement at 405 nm. Preincubation of test serawith non-labelled GAD₆₅ (at final concentration from 0.0005 to 0.01μg/mL) prior to performing the ELISA resulted in a dose dependentreduction of OD 450 nm values. These experiments confirmed thespecificity of the GAD₆₅ autoantibody ELISA based techniques accordingto the present invention.

In the case of n=14 sera from patients with Graves' disease, OD 450 nmvalues for all samples were below 0.05 (<1 ELISA unit/mL in ELISA basedtechniques according to the present invention); all these samples werenegative for GAD₆₅ autoantibodies in RIA (<1 RIA unit/mL).

Comparison of the lowest detection limit for GAD₆₅ autoantibodies inELISA based techniques according to the present invention and RIA isshown in Table 2. In the RIA dilutions of WHO reference preparation forislet cell autoantibodies [NIBSC 97/550] from 250 to 31.25 WHO units/mL,detectable levels of GAD₆₅ autoantibodies were seen. However, in theELISA based techniques according to the present invention, GAD₆₅autoantibodies were detectable in the case of WHO standard dilutionsfrom 250 to 3.91 WHO units/mL. Further, an example of the dilutionprofile of a serum sample Z (from a patient with high levels of GAD₆₅autoantibodies) is shown in Table 2. In the case of RIA, GAD₆₅autoantibodies were detectable in the sample Z in the range from 1/8 to1/8192 dilution. In the case of ELISA based techniques according to thepresent invention, GAD₆₅ autoantibodies were detectable in the rangefrom 1/8 to 1/32768 dilution. Consequently, the end point dilutionanalyses of WHO standard and patient's serum indicated that a 4-fold to8-fold greater dilutions were detectable in ELISA based techniquesaccording to the present invention compared to RIA.

An example of results of IA-2 autoantibody measurement by ELISA basedtechniques according to the present invention is shown in Table 3.Typical OD 450 nm values for the set of IA-2 autoantibody calibrators(0, 1.0, 2.0, 4.0, 8.0, 16, 32, 64, 128 ELISA units/mL) were from 0.054to >4.0 and OD405 values were from 0.008 to 1.874. Sera from n=10patients with type 1 diabetes mellitus who had IA-2 autoantibody levelsin RIA from 2.0 to 38.9 RIA units/mL were all positive in ELISA basedtechniques according to the present invention. These samples gave OD 450nm values between 0.209 to >4.0 (2.6 to >32 ELISA units/mL). WHOstandard was detectable in IA-2 autoantibody RIA at 250 WHO units/mL and125 WHO units/mL however, further dilutions (62.5 WHO units/mL and 31.25WHO units/mL) were detectable in ELISA based techniques according to thepresent invention. OD 450 nm values in the case of n=10 sera fromhealthy blood donors (all negative for IA-2 autoantibodies in RIA) werebetween 0.030 and 0.071 (<1 ELISA unit/mL).

Results of a combination assay for GAD₆₅ autoantibodies and IA-2autoantibodies are shown in Tables 4 and 5. Table 4 shows results ofcombined measurement of GAD₆₅ autoantibodies and IA-2 autoantibodies inELISA based techniques according to the present invention, when IA-2-Bior GAD₆₅-Bi or IA-2-Bi plus GAD₆₅-Bi were used in the assay. In the caseof IA-2 autoantibody calibrators, no signal in the ELISA basedtechniques according to the present invention was detected when GAD₆₅-Biwas used, whereas dose dependent increase of OD 450 nm was observed whenIA-2-Bi or IA-2-Bi plus GAD₆₅-Bi were used. The OD 450 nm signal withIA-2-Bi alone was essentially the same as signal with IA-2-Bi plusGAD₆₅-Bi. In the case of GAD₆₅ autoantibody calibrators, no signal wasdetected when IA-2-Bi was used in the assay while dose dependentresponse of OD 450 nm was observed with GAD₆₅-Bi and IA-2-Bi plusGAD₆₅-Bi. The OD 450 nm signals in the case of GAD₆₅-Bi alone andIA-2-Bi plus GAD₆₅-Bi plus GAD₆₅-Bi were comparable. Measurement of bothautoantibodies in different dilutions of serum sample Z showed a goodagreement with the results of IA-2 autoantibodies or GAD₆₅autoantibodies alone. Serum from an individual healthy blood donor orhealthy blood donor pool serum gave very low OD 450 nm values from 0.006to 0.046 irrespective of which biotinylated antigen was used. Thisexperiment shows that in the combined assay to measure IA-2autoantibodies and GAD₆₅ autoantibodies, the results are specific andreflect the presence of the two autoantibodies in the test sample.

More detailed results of the combined measurement of IA-2 autoantibodiesand GAD₆₅ autoantibodies are shown in Table 5. Sera from patients withType 1 diabetes were tested in the assay. IA-2 autoantibodies and GAD₆₅autoantibodies were assessed in these sera by RIA; sera 1-3 werepositive for both IA-2 autoantibodies and GAD₆₅ autoantibodies, sera 4-6were negative for GAD₆₅ autoantibodies but positive for IA-2autoantibodies, sera 7-9 were positive for GAD₆₅ autoantibodies butnegative for IA-2 autoantibodies and sera 10-12 were negative for bothIA-2 or GAD₆₅ autoantibodies. As shown in Table 5, in the combined assayone or the other or both autoantibodies were detected in serum samples.Furthermore, in the case of serum 6 that had borderline levels of IA-2autoantibodies by RIA (0.9 RIA units/mL), the signal in the combinedELISA based techniques according to the present invention was clearlypositive.

Additional examples of results with ELISA for GAD₆₅ autoantibodies, IA-2autoantibodies and combined GAD₆₅ and IA-2 autoantibodies according tothe present invention for different patient subgroups are shown inTables 6, 7 and 8 respectively.

CONCLUSIONS

The above results show that the non-radioactive based techniquesaccording to the present invention allow measurement of GAD₆₅autoantibodies in test samples. The non-radioactive based techniquesaccording to the present invention can also be employed to measure IA-2autoantibodies separately or simultaneously. The measurements arespecific and they are in agreement with the results of GAD₆₅autoantibodies and IA-2 autoantibodies measurements by establishedradioactive reference methods (M Powell, L Prentice, T Asawa, R Kato, JSawicka, H Tanaka, V Petersen, A Munkley, S Morgan, B Rees Smith, JFurmaniak. Clinica Chimica Acta, 1996 256: 175-188; and M Masuda, MPowell, S Chen, C Beer, P Fichna, B Rees Smith, J Furmaniak.Autoantibodies to IA-2 in insulin-dependent diabetes mellitus.Measurements with a new immunoprecipitation assay. Clinica Chimica Acta,2000 291: 53-66). Furthermore, measurements of GAD₆₅ autoantibodies andIA-2 autoantibodies by non-radioactive based techniques according to thepresent invention are at least as sensitive compared to results by RIA(Tables 1, 2 and 3).

The techniques according to the present invention provide anon-radioactive assay to measure GAD₆₅ autoantibodies or IA-2autoantibodies with a high sensitivity that is convenient to use fordiagnostic and screening purposes. A combination assay for GAD₆₅ andIA-2 autoantibodies according to the present invention can be ofparticular benefit for use in large population screening programmes.

TABLE 1 GAD₆₅ autoantibodies in patient sera in ELISA according to thepresent invention and radioimmunoassay (RIA) based on ¹²⁵1-labelledGAD₆₅ ELISA ELISA RIA Sample units/mL OD450 nm OD405 nm RIA units/mLSerum Samples— Type I DM 1 10.7 0.980 0.254 <1.0 2 8.1 0.660 0.158 <1.03 2.1 0.183 0.024 <1.0 4 1.3 0.117 0.001 <1.0 5 4.4 0.432 0.091 <1.06 >128 >4.0 2.100 74.3 7 >128 >4.0 2.283 118.8 8 >128 >4.0 2.155 83.29 >128 >4.0 2.230 87.4 10 >128 >4.0 2.023 83.0 11 >128 >4.0 1.774 41.912 >128 >4.0 1.554 26.8 13 105.8 3.596 1.060 7.5 14 21.9 1.830 0.485 3.615 20.2 1.735 0.466 3.1 16 12.0 1.116 0.290 1.5 17 43.4 2.615 0.732 4.718 20.8 1.771 0.473 2.2 Serum Samples— Graves' 1 <1.0 0.015 <1.0 2 <1.00.019 <1.0 3 <1.0 0.049 <1.0 4 <1.0 0.048 <1.0 5 <1.0 0.008 <1.0 6 <1.00.031 <1.0 7 <1.0 0.036 <1.0 8 <1.0 0.033 <1.0 9 <1.0 0.029 <1.0 10 <1.00.037 <1.0 11 <1.0 0.036 <1.0 12 <1.0 0.042 <1.0 13 <1.0 0.041 <1.0 14<1.0 0.047 <1.0 Footnote: GAD Ab levels above 1 RIA unit/mL wereconsidered positive by RIA. Type 1 DM = Type 1 diabetes mellitus.Graves' = Graves' disease.

TABLE 2 Comparison of the sensitivity of the GAD₆₅ Ab measurement inELISA and in RIA. ELISA ELISA RIA Sample units/mL OD450 nm OD405 nm RIAunits/mL WHO Standard (97/550)* 250 >128 >4.0 1.234 6.4 125 45.5 2.6700.742 3.6 62.5 17.4 1.557 0.422 2.5 31.25 10.0 0.894 0.225 1.1 15.63 4.40.431 0.095 <1.0 7.81 2.2 0.202 0.023 <1.0 3.91 1.2 0.100 0.00 <1.0 1.95<1.0 0.058 0.00 <1.0 0.98 <1.0 0.031 0.00 <1.0 Sample Z 1/8   >128 >4.02.048 91 1/32  >128 >4.0 1.868 76 1/128  >128 >4.0 1.769 381/512  >128 >4.0 1.591 13 1/1024 90 3.714 1.120 5.6 1/2048 29.4 2.5423.1 1/4096 12.0 1.375 1.4 1/8192 6.9 0.784 1.0  1/16384 2.8 0.385 <1.0 1/32768 1.6 0.210 <1.0  1/65536 <1.0 0.132 <1.0  1/131072 <1.0 0.092<1.0  1/262144 <1.0 0.055 <1.0 Footnote: GAD Ab levels above 1 RIAunit/mL were considered positive in RIA. *WHO units/mL.

TABLE 3 Measurement of IA-2/ICA512 autoantibodies in ELISA and in RIAbased on ¹²⁵I -labelled IA-2/ICA512. ELISA ELISA RIA Sample units/mLOD450 nm OD405 nm RIA units/mL IA-2Ab Calibrator 0 0.054 0.008 1 0.1140.021 2 0.183 0.040 4 0.313 0.073 8 0.614 0.166 16 1.219 0.340 32 2.5060.719 64 >4 1.371 128 >4 1.874 Serum sample— Type 1 DM 1 >32 >4 1.42014.8 2 >32 >4 1.594 38.9 3 11.2 0.859 0.228 2.8 4 >32 >4 2.096 22.75 >32 >4 2.348 33.9 6 6.5 0.516 0.140 6.3 7 >32 >4 2.354 15.8 8 4.10.265 0.067 2.9 9 2.6 0.209 0.055 2.3 10 8.4 0.664 0.179 2.0 WHOStandard (97/550)* 250 18.8 1.503 2.0 125 9.2 0.721 1.2 62.5 4.0 0.337<1.0 31.25 2.0 0.191 <1.0 15.63 <1.0 0.116 <1.0 7.81 <1.0 0.093 <1.0Individual Healthy Blood Donors 1 <1.0 0.030 <1.0 2 <1.0 0.036 <1.0 3<1.0 0.043 <1.0 4 <1.0 0.045 <1.0 5 <1.0 0.070 <1.0 6 <1.0 0.045 <1.0 7<1.0 0.063 <1.0 8 <1.0 0.037 <1.0 9 <1.0 0.071 <1.0 10 <1.0 0.069 <1.0Footnote: IA-2/ICA512 Ab levels above 1 RIA unit/mL were consideredpositive in RIA. Type 1 DM = Type 1 diabetes mellitus. *WHO units/mL.

TABLE 4 Combined GAD₆₅ Ab and IA-2/ICA512 Ab measurements in ELISA.GAD₆₅-Bi + Sample IA-2-Bi GAD₆₅-Bi IA-2-Bi ELISA units/mL OD450 nm OD450nm OD450 nm IA-2 Ab Calibrator 8 1.314 0.022 1.252 16 2.730 0.033 2.57432 3.888 0.031 3.824 GAD65 Ab Calibrator 4 0.053 0.460 0.458 16 0.0451.518 1.400 32 0.043 2.033 2.160 Serum Sample Z Diluted 1/2 3.069 >4 >41/4  2.328 >4 >4 1/8  0.905 >4 >4 1/16 0.401 3.936 3.875 1/32 0.1973.379 3.626 1/64 0.143 2.209 2.512  1/128 0.069 1.718 1.571 IndividualHealthy 0.019 0.006 0.023 Blood Donor Serum Healthy Blood 0.022 0.0150.046 Donor Serum Pool

TABLE 5 Combined GAD₆₅ Ab and IA-2/ICA512 Ab measurements in ELISA.Sample IA-2/ICA512 ELISA GAD₆₅Ab RIA Ab RIA units/mL OD450 nm OD405 nmRIA units/mL RIA units/mL GAD65 Ab Calibrator 0 0.080 0.028 2 0.2310.070 8 0.737 0.219 16 1.476 0.436 32 2.117 0.613 64 2.648 0.755 1283.607 1.083 IA-2 Ab Calibrator 0 0.065 0.025 2 0.205 0.054 4 0.308 0.0818 0.552 0.154 16 1.116 0.327 32 2.031 0.590 64 3.596 1.079 128 >4 1.777Serum samples— type 1 DM 1 >4 1.646 10.8 14.8 2 >4 1.964 50.2 39.0 31.640 0.481 3.1 2.8 4 >4 1.927 Neg 22.7 5 >4 2.428 Neg 39.9 6 0.2980.100 Neg 0.9 7 3.594 1.063 26.8 Neg 8 >4 2.092 253.0 Neg 9 1.874 0.5542.2 Neg 10 0.068 0.040 Neg Neg 11 0.074 0.029 Neg Neg 12 0.066 0.021 NegNeg Healthy Blood 0.073 0.020 Neg Neg Donor Serum Pool Footnote: GAD₆₅Ab levels above 1 RIA unit/mL were considered positive in RIA.IA-2/ICA512 Ab levels above 1 RIA unit/mL were considered positive inRIA. Type 1 DM = Type 1 diabetes mellitus.

TABLE 6 GAD₆₅ Ab measured in different patient groups by ELISA orradioimmunoassay (RIA) based on ¹²⁵I-labelled GAD65. ELISA RIA numberpositive (%) number positive (%) (5 units/mL (25 units/mL or greater =positive) or greater = positive) Healthy blood donors 2/300 (0.7%)¹ 3/300 (1%)² n = 300 Type 1 DM 39/39 (100%)³   32/39 (82%)⁴ n = 39 Type 2DM 1/62 (1.6%)⁵  0/62 (0%) n = 62 Graves' disease 2/88 (2.3%)⁶   3/88(3.4%)⁷ n = 88 Hashimoto's thyroditis 1/11 (9%)⁸   0/11 n = 11Rheumatoid arthritis 0/10 0/10 n = 10 Systemic lupus erythematosus 1/10(10%)⁹   1/10 (10%)⁹ n = 10 ¹Values of samples positive in GAD₆₅ AbELISA were 11 units/mL and >500 units/mL (all units/mL are WHO 97/550).Adsorption experiments indicated the presence of specific GAD₆₅ Ab. Thesame samples were negative and 2500 units/mL in the RIA respectively.²Values of samples positive in GAD₆₅ Ab RIA were 33, 100 and 2500units/mL. The same samples were negative, negative and > 500 units/mL inthe ELISA respectively. ³Range of values: 5.2-greater than 500 units/mL.⁴Range of values: negative-3800 units/mL. ⁵Value of a sample positive inGAD₆₅ Ab ELISA was 40 units/mL. The same sample was negative in the RIA.⁶Values of samples positive in GAD₆₅ Ab ELISA were 306 and 500 units/mL.The same samples were 354 units/mL and 1700 units/mL in the RIA,respectively. ⁷Values of samples positive in GAD₆₅ Ab RIA were 78, 354and 1700 units/mL. The same samples were negative, 306 and 500 units/mLin the ELISA, respectively. ⁸Value of a sample positive in GAD₆₅ AbELISA was 24 units/ml; this sample was negative in the RIA. ⁹The samesample was positive in GAD₆₅ Ab ELISA and RIA with values of 15 units/mLand 30 units/mL, respectively.

TABLE 7 IA-2 Ab measured in different patient groups by ELISA orradioimmunoassay (RIA) based on ¹²⁵I-labelled IA-2. ELISA RIA numberpositive (%) number positive (%) (30 units/mL (125 units/mL or greater =positive) or greater = positive) Healthy blood donors  2/210 (1%)¹ 2/210 (1%)² n = 210 Type 1 DM 12/30 (40%)³ 12/30 (40%)⁴ n = 30 Type 2DM  1/62 (1.6%)⁵  0/62 n = 62     Graves' disease  0/102  0/102 n = 102    Rheumatoid arthritis  0/10  0/10 n = 10     Systemic lupuserythematosus  0/10  0/10 n = 10     ¹Values of samples positive in IA-2Ab ELISA were 44 units/mL and 179 units/mL (units/mL are WHO 97/550).Adsorption experiments indicated the presence of specific IA-2 Ab inthese samples. The same samples were negative in the RIA. ²Values ofIA-2 Ab positive samples in RIA were 150 units/mL and 288 units/mL. Thesame samples were negative in the ELISA. ³Range of values: 132 −> 4000units/mL. ⁴Range of values: 178 − 4508 units/mL. ⁵Value of IA-2 Abpositive sample was 101 units/mL. This sample was negative in the RIA.

TABLE 8 GAD₆₅ Ab ELISA, IA-2 Ab ELISA and combined GAD₆₅ Ab + IA-2 AbELISA results in different patient groups. number positive (%) GAD₆₅ AbIA-2 Ab GAD₆₅ Ab + ELISA ELISA IA-2 Ab ELISA Type 1 DM 28/35¹ 14/35²33/35³ n = 35 (80%) (40%) (94.3%) Type 2 DM 1/44⁴ 1/44⁵ 2/44⁶ n = 44(2.3%) (2.3%) (4.5%) Healthy blood donors 2/73⁷ 0/73 2/73⁸ n = 73 (2.7%)(0%) (2.7%) Graves' disease 0/20 0/20 0/20 n = 20 (0%) (0%) (0%)Rheumatoid arthritis 0/10 0/10 0/10 n = 10 (0%) (0%) (0%) Systemic lupuserythematosus 1/10⁹ 0/10 1/10¹⁰ n = 10 (10%) (0%) (10%) ¹Value of GAD65Ab for samples positive in ELISA ranged from 7.3->500 units/mL (units/mLare WHO 97/550). ²Values of IA-2 Ab for samples positive in ELISA rangedfrom 34-3613 units/mL (units/mL are WHO 97/550). ³All combined ELISAresults were expressed as index calculated as follows:$\frac{{OD}_{450\mspace{11mu}{nm}}\mspace{14mu}{of}\mspace{14mu}{sample}}{{OD}_{450\mspace{11mu}{nm}}\mspace{14mu}{of}\mspace{14mu}{pool}\mspace{14mu}{of}\mspace{14mu}{healthy}\mspace{14mu}{blood}\mspace{14mu}{donor}\mspace{14mu}{sera}};$values of 2.0 or greater are positive 18 sera were positive for GAD65 Aband negative for IA-2 Ab; all 18 were positive in the combined ELISA. 4sera were positive for IA-2 Ab and negative for GAD65 Ab; all 4 werepositive in the combined ELISA 10 sera were positive for GAD65 Ab andfor IA-2 Ab; all 10 were positive in the combined ELISA 1 serum wasnegative for GAD65 Ab and for IA-2 Ab but positive in the combined ELISA2 sera were negative in all 3 assays. ⁴GAD65 Ab levels were 10 units/mLand IA-2 Ab were negative in the one positive sample. ⁵GAD65 Ab werenegative and IA-2 Ab levels were 76 units/mL in the one positive sample.⁶The positive samples were the same as described in 4 and 5 (index value7.8 and 4.8 respectively). GAD65 Ab ELISA, IA-2 Ab ELISA and combinedGAD65 Ab + IA-2 Ab ELISA results in different patient groups. ⁷GAD65 Ablevels were 9 and >500 units/mL but IA-2 Ab were negative in the twopositive samples. ⁸The positive samples were the same as described in 7.The index values for these samples were: 3.6 and 55.0 respectively.⁹GAD65 Ab levels were 15 units/mL but IA-2 Ab were negative. ¹⁰Thepositive sample was the same as described in 9. The index value was 6.0.

The invention claimed is:
 1. A method of screening a diluted sample ofserum or plasma obtained from an animal subject for analyteautoantibodies reactive with one or more antigenic molecules selectedfrom glutamic acid decarboxylase (GAD) antigens or the protein tyrosinephosphatase-like islet cell antigen (IA-2), said method comprising: (a)immobilizing antigenic molecules from one or more first sources to asolid support in an amount so as to form a monovalent intermediatecomplex comprising [antigenic molecule of said first source]-[analyteautoantibody] capable of forming a divalent complex with antigenicmolecules of a second source, wherein said antigenic molecules from theone or more first sources are capable of interacting with analyteautoantibodies in a sample of serum or plasma from said subject, or acalibrator and comprises molecules selected from the group consisting ofglutamic acid decarboxylase 65 (GAD65), glutamic acid decarboxylase 67(GAD67), and IA-2; (b) contacting said immobilized antigenic moleculesfrom the one or more first sources with: (1) a diluted sample of serumor plasma from said subject, wherein the sample is diluted 32-fold orless; or said calibrator; and (2) antigenic molecules from one or moresecond sources comprising a direct or indirect label, wherein saidantigenic molecules from the one or more second sources are capable ofinteracting with analyte autoantibodies in a sample of serum or plasmafrom said subject, or said calibrator and comprises molecules selectedfrom the group consisting of GAD65; GAD67; IA-2, whereby analyteautoantibodies when present in said sample or calibrator interact withsaid antigenic molecules from the one or more first and second sourcesto form one or more divalent complexes comprising [antigenic molecule ofsaid first source]-[analyte autoantibody]-[antigenic molecule of saidsecond source]; and (c) detecting the presence of complexes formed in(b) to provide an indication of analyte autoantibodies present in saidsample; wherein said antigenic molecules from the one or more first andsecond sources comprises at least one GAD antigenic molecule.
 2. Themethod according to claim 1, wherein said immobilised antigenicmolecules of the one or more first sources are subsequently contactedwith the sample obtained from said subject either simultaneously orseparately to said antigenic molecules of said one or more secondsources.
 3. The method according to claim 1, wherein said immobilisedantigenic molecules of said one or more first sources are subsequentlycontacted with the sample obtained from said subject so as to form anintermediate complex comprising [antigenic molecule]-[analyteautoantibody] where the antigenic molecule is immobilised to a solidsupport and the thus formed immobilised intermediate complexes issubsequently contacted with said antigenic molecules of said one or moresecond sources, present in solution phase, so as to form said complexescomprising [antigenic molecule]-[analyte autoantibody]-[antigenicmolecule of said second source] immobilised to a solid support via anantigenic molecule of the one or more first sources.
 4. The methodaccording to claim 1 wherein said antigenic molecules from the one ormore first sources are provided in an amount so as to form a monovalentintermediate complex comprising [antigenic molecule]-[analyteautoantibody]-capable of forming a divalent complex with antigenicmolecules of said one or more second sources wherein said divalentcomplex comprises [antigenic molecule of said first source]-[analyteautoantibody]-[antigenic molecule of said second source].
 5. The methodaccording to claim 1, wherein the sample is diluted 16-fold or less. 6.The method according to claim 1, wherein the calibrator is diluted32-fold or less.
 7. The method according to claim 1, wherein thecalibrator is diluted 16-fold or less.
 8. The method according to claim1, wherein the calibrator is diluted 8-fold or less.
 9. The methodaccording to claim 1, wherein the label comprises an enzymatic label.10. The method according to claim 1, wherein the label comprisesalkaline phosphatases, horse radish peroxidase or biotin.
 11. The methodaccording to claim 1, wherein the antigenic molecules of said one ormore first and second sources when present in said one or more complexescomprise one or more of the same antigenic molecules.
 12. The methodaccording to claim 1, wherein the antigenic molecules of said one ormore first and/or second sources comprises fusion molecules.
 13. Themethod according to claim 1, wherein both antigenic molecules of saidfirst and second sources when present in the one or more complexes, eachcomprise at least one antigenic molecule that is the same, with whichanalyte autoantibodies when present in said sample can interact.
 14. Themethod according to claim 1, wherein said sample of serum or plasma isobtained from an animal subject suspected of suffering from, susceptibleto or having one or more of the following: type 1 diabetes mellitusand/or stiff man syndrome, type 2 diabetes mellitus, one or moreautoimmune thyroid diseases, celiac disease, one or more connectivetissue diseases, adrenal autoimmunity, or a combination of two or moredifferent autoimmune diseases.
 15. The method according to claim 1,wherein the antigenic molecules from the one or more first sourcesconsist essentially of GAD65 or GAD67.
 16. The method according to claim1, wherein the antigenic molecules from the one or more first sourcesconsist essentially of GAD65 and GAD67.
 17. The method according toclaim 1, wherein the antigenic molecules from the one or more secondsources consist essentially of GAD65 or GAD67.
 18. The method accordingto claim 1, wherein the antigenic molecules one or more second sourcesconsist essentially of GAD65 and GAD67.
 19. The method according toclaim 1, wherein the antigenic molecules of said one or more firstsources comprises GAD65 or the antigenic molecules of said one or moresecond sources comprises GAD67.
 20. The method according to claim 1,wherein the antigenic molecules of said one or more first sourcescomprise GAD67 or the antigenic molecules of said one or more secondsources comprises GAD65.
 21. The method according to claim 1, whereinantigenic molecules of said one or more first and second sources whenpresent in the one or more complexes comprise GAD65 or GAD67.
 22. Themethod according to claim 1, wherein the antigenic molecules of said oneor more first or second sources when present in the one or morecomplexes comprise GAD65 or GADA67.
 23. The method according to claim 1,wherein the antigenic molecules of said one or more first and secondsources when present in the one or more complexes comprise GAD65 andGAD67.
 24. The method according to claim 1, wherein the antigenicmolecules of said one or more first or second sources when present inthe one or more complexes comprise GAD65 and GAD67.
 25. The methodaccording to claim 1, wherein both antigenic molecules of said one ormore first and second sources when present in the one or more complexescomprise a variant, analogue, derivative or fragment, which may be thesame or different, of GAD65 or GAD67, with which analyte autoantibodieswhen present in said sample can interact.
 26. The method according toclaim 1, wherein one antigenic molecules of said one or more first orsecond source when present in the one or more complexes comprise GAD65or GAD67, the other antigenic molecule when present in the one or morecomplexes comprises GAD65 or GAD67, with which analyte autoantibodieswhen present in said sample can interact.
 27. The method according toclaim 1, wherein both antigenic molecules of said one or more first andsecond sources when present in the one or more complexes comprise IA-2,with which analyte autoantibodies when present in said sample caninteract.
 28. The method according to claim 1, wherein one antigenicmolecules of said one or more first or second source when present in theone or more complexes comprise IA-2, the other antigenic molecule whenpresent in the IA-2, with which analyte autoantibodies when present insaid sample can interact.
 29. The method according to claim 1, whereinthe antigenic molecules of said one or more first and second sourcescomprise of IA-2.
 30. The method according to claim 1, wherein theantigenic molecules of said one or more first or second sources compriseof IA-2.
 31. The method according to claim 1, wherein the antigenicmolecules of said one or more first or second sources when present inone or more complexes comprise IA-2.
 32. The method according to claim1, wherein the antigenic molecules of said one or more first and secondsources when present in one or more complexes comprise IA-2.
 33. Themethod according to claim 1, wherein the antigenic molecules of thefirst or second sources consist essentially of GAD65 and IA-2.
 34. Themethod according to claim 1, wherein the antigenic molecules of thefirst or second sources consist essentially of GAD67 and IA-2.